W.&L.E.  GURLEY 


Ol 


UNIVERSITY  OF  CALIFORNIA 

DEPARTMENT  OF  CIVIL.  ENGINEERING 

BERKELEY.  CALIFORNIA 


A    MANUAL 

OF   THE    PRINCIPAL 

INSTRUMENTS 

USED  IN 

AMERICAN  ENGINEERING 
AND  SURVEYING 


MANUFACTURED   BY 

W.   &  L.   E.   GURLEY 

TROY,  N.  Y.,  U.  S.  A. 


FORTY-EIGHTH   EDITION 
PRICE  ONE  DOLLAR 


PUBLISHED    BY 

W.  &  L.  E.  GURLEY 

TROY,   N.  Y. 
1921 


I?*-/ 

Library  ° 


^Library 

Entered,  according  to  Act  of  Congress,  in  the  Year  1911 

By  W.   &  L.   E.   GURLEY 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington 

COPYRIGHT,   1912 
By  W.   &  L.   E.   GURLEY 

COPYRIGHT,   1914 
By  W.   &  L.   E.   GURLEY 

COPYRIGHT,  1921 
By  W.   &  L.   E.   GURLEY 


OFFICE  &\VORI« 


\V&L.E.GURLEY 


Engineering 
Library 


GrURLEY'S  MANUAL 
is  primarily  a  book 
of  instructions  in  the 
adjustment   and  use 
of  field  instruments. 

Simplicity  of  ex- 
pression is  sought 
and  no  attempt  is 
made  at  treatises 
which  are  more 
properly  to  be  found 
in  technical  publica- 
tions. 


800336 


PREFACE 

IN  presenting  this  edition  of  our  Manual  we  offer  the 
engineering  profession  many  new  field  instruments, 

new  features  and  refinements,  resulting  from  con- 
tinuous effort  and  study  for  a  period  of  seventy-five 
years.  The  House  of  W.  &  L.  E.  Gurley  is  the  largest 
as  well  as  the  oldest  American  manufacturer  of 
engineering  instruments  and  our  line  is  the  most  desir- 
able and  also  the  most  complete  of  its  kind  in  the  world. 

The  merit  of  any  article  is  fully  determined  by  its 
ability  to  stand  the  test  of  time,  and  the  service  given 
by  GURLEY  INSTRUMENTS  for  three-quarters  of  a  century 
proves  that  they  possess  those  characteristics  which 
qualify  them  for  the  most  exacting  demands  of  modern 
engineering  practice. 

In  our  zeal  for  offering  only  the  best  we  have  looked 
beyond  the  vision  of  commercialism  and  our  entire 
organization  takes  great  pride  in  our  finished  products 
as  they  leave  our  hands  to  fulfill  their  mission  of  locat- 
ing, developing  and  conserving  the  resources  of  nature 
and  the  upbuilding  of  those  projects  which  tend  to  the 
welfare  and  comfort  of  mankind. 

W.  &  L.  E.  GURLEY. 


LIST  OF  ILLUSTRATIONS 

FIG.  ILLUSTRATION  PAGE 

1.  Cross  Section  of  Transit 24 

2.  No.  154  showing  Dust  Guard  for  Objective.  .  26 

3.  Platinum  Cross  Wires 28 

4.  One  Piece  Truss  Standard 30 

5.  Radially  Ribbed  and  Dished  Limb  and  Plate 

and   Tapered   Centers 32 

6.  Top    Plate    of    the    Light    Mountain    Transit, 

showing  location  of  verniers,  levels,  varia- 
tion arc  pinion,  and  needle  lifter  screw.  ...  33 

7.  Limb  1 36 

8.  Limb  IV 37 

9.  No.  149  Beaman  Stadia  Arc 40 

10.  No.  27-A  Precise  Transit 44 

11.  No.   10- A  Precise  Transit 4^ 

12.  View  of  Hell  Gate  Bridge  during  construction  48 

13.  No.  18-A  Precise  Transit,  Hell  Gate  Model.  .  49 

14.  No.   10-A-3  Precise  Transit  with  three  screw 

leveling  head 53 

15.  No.  28  Light  Mountain  Transit 55 

16.  No.  20-A  Explorers  Precise  Transit 57 

17.  Explorers    Transit    with    its    special    jointed 

Extension    tripod,    canvas    carrying    case, 

and  leather  covered  wooden  box 58 

Explorers    Transit,    with    its    special    tripod, 

packed  in  a  dress  suit  case  24  in.  long.  ...  59 

19.  No.   102   Reconnoissance   Transit 61 

20.  Stadia   Constant    (Diagram) 71 


16  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

FIG.  ILLUSTRATION  PAGE 

21.  Diagram  (To  adjust  line  of  collimation)  .  ...  78 

22.  No.   136  Vertical  Circle  with  No.  141   Alum- 

inum   Guard 85 

23.  No.   138  Vertical   Circle    with    two    opposite 

double  verniers,  and  guard 86 

24-.     No.  139  Vertical  Circle,  4.5  in.  diameter  with 
graduations  on  edge  or  rim,  protected  by  a 

metal  guard.      Circle,  etc 87 

25.  No.  139-A,  139-B  and  140  Vertical  Arcs.  ...  88 

26.  No.  145  Level  on  Telescope 89 

27.  Graduations   of   Beaman  Stadia  Arc 92 

28.  No.  150  Gradienter 96 

29.  No.   160-161     Detachable    Side    and    Riding 

Telescopes    for    vertical    sighting    in    mine 

surveying 101 

30.  No.   165-166    Cross    Wire    Illuminating    Re- 

flectors     103 

31.  No.  168  Diagonal  Prism 103 

32.  No.  170  Plummet  Lamp    104 

33.  No.  180  Attached  Magnifiers    106 

34.  No.  192  Solar  Screen 106 

35.  No.  190  Burt  Solar  Attachment 115 

36.  No.  30-A    Precise    Transit    with    Burt    Solar 

Attachment    119 

37.  No.  196  Striding  or  Adjusting  Level 123 

38.  No.  32-A   Precise    Transit 138 

39.  No.  226  Vernier    Compass    150 

40.  No.  241  Leveling  Adopter    . 158 

41.  No.  242  Leveling    Head    159 


LIST  OF  ILLUSTRATIONS  17 

FIG.  ILLUSTRATION  PAGE 

42.  No.  262   Telescopic  Sight   160 

43.  Compass     fitted     with     No.     262      Telescopic 

Sight,  etc 162 

44.  No.  294  Compass    167 

45.  No.  285  Compass    168 

46.  No.  335  Geologists  Compass    171 

47.  No.  341-A  Dip  Compass    174 

48.  No.  350  Dial   Compass    176 

49.  No.  3154  Wood  Box  Pocket  Compass 180 

50.  No.  375-377  Engineers  Wye  Levels 182 

51.  Sectional  View  of  Engineers  Wye  Level.  ...  183 

52.  No.  378  Engineers  Wye  Level 1 84 

53.  View  of  Engineers  Wye  Level,  etc 185 

54.  No.  381  Architects  Level  • 189 

55.  No.  384  Explorers   Level    197 

56.  No.  643  Locke  Hand  Level    202 

57.  No.  646  Abney  Hand  Level 203 

58.  No.  640  Monocular  Hand  Level 204 

59.  No.  500  Philadelphia     Rod    with     Micrometer 

Target    210 

60.  No.  500-R     Philadelphia     Service     Rod     with 

Oval  Target    211 

61.  No.  500-B  Philadelphia  Rod   212 

62.  No.  501  Philadelphia   Rod    213 

63.  No.  501-B   Self-Reading   Rod    214 

64.  No.  505  New  York  Rod 215 

65.  No.  510  and  511  Architects  Rods    .                    .  216 


18  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

FIG.  ILLUSTRATION  PAGE 

66.  No.  517  Slip   Jointed   Rod    217 

67.  Front  and  Rear  View  of  No.  517  Slip  Jointed 

Rod,   showing  joints    217 

68.  No.  514-B  and  514-C   Stadia  Rod    218 

69.  No.  514-D  and  514-E  Stadia  Rod    218 

70.  View  of  Hinges,  ribbed  brace   and  clamp   of 

Telemeter  or  Stadia  Rod    219 

71.  No.  513  Telemeter  or   Stadia   Rod    .  .  .  ^  £,*^_.    220 

72.  No.  516  Cross  Section   Rod    221 

73.  View  of  Hinged  Joint    222 

74.  No.  524-A  Plain  Leveling  Rod  without  Target  223 

75.  View  of  Clamp   of   Plain   Two   Ply   Leveling 

Rods   223 

76.  Rear    View    of    Lower    Portion    of    Four    Ply 

Rod  No.  524-A 223 

77.  No.  522-A  Plain  Two  Ply  Leveling  Rod. 224 

78.  No.  551-R  Molitor  Precise  Rod,  Front  View.  .  224 

79.  No.  551-R  Molitor  Precise  Rod,  Rear  View.  .  .  224 

80.  No.  552-R  Self   Reading  Tape  Leveling  Rod, 

front     225 

81.  No.  552-R  Self   Reading  Tape  Leveling  Rod, 

side     225 

82.  Precise    Leveling    Rod 227 

83.  Nos.  525-B  to  528  Flexible  or  Pocket  Level- 

ing Rods    229 

84.  No.530,    531     Combined    Leveling    Pole    and 

Flagstaff    230 

85.  No.  534  to  536  Wooden  Flagstaff 230 


LIST  OF  ILLUSTRATIONS  19 

FIG.  ILLUSTRATION  PAGE 

86.  Nos.  540-A  to   544   Iron  and  Steel  Ranging 

Poles 231 

87.  Nos.  537-A  to  538-B  Flagstaffs 232 

88.  No.  545  Rod  Level  as  applied  to  a  Rod 233 

89.  No.  546  Rod  Level 234 

90.  No.  547  Rod  Level    235 

91.  No.  548  Rod  Level    236 

92.  Nos.  415,  416,  400  and  430  Solid  Round  Leg 

Tripods    238 

93.  Nos.  405,  435,  410,  440  Split  and  Extension 

Leg  Tripods    239 

94.  Nos.  412  and  443  Jointed  Extension  Leg  Tri- 

pods for  Explorers  Transits  and  Levels.  .  .  241 

95.  No.  576-C  Plane  Table  Outfit,  etc 244 

96.  No.  570  Johnson  Plane  Table  Outfit 245 

97.  No.  584-C  Telescopic  Alidade,  etc 246 

98.  No.  592-C  Explorers  Alidade,  etc 249 

99.  No.  586  Traverse  Plane  Table  Outfit 257 

100.  Traverse  Plane  Table  Movement,  etc 250 

101.  No.  590-A  Pocket  Sight  Alidade 259 

102.  No.  594  Army  Sketching  Case 261 

103.  Showing     Method     of     using     Fiala     Scout 

Sketching  Case 264 

104.  No.  596  Fiala  Scout  Sketching  Case 266 

105.  Nos.  450  to  458  Plain  Plummets 272 

106.  Adjustable  Plummet  showing  Details  of  Con- 

cealed Reel,  No.  465   273 

107.  No.  616  Acoustic  Current  Meter  Outfit 277 

108.  No.  623  Electric  Current  Meter  Outfit,  etc.  .  279 


20  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

FIG.  ILLUSTRATION  PAGE 

109.  No.  623  Electric  Current  Meter  Outfit,  etc.  .  280 

110.  No.  609  Electric  Register 281 

111.  No.  628  Hook  Gage 283 

112.  Section    of    Paper    Tape,    showing    printed 

record,  made,  etc 289 

113.  No.  630  Printing  Water  Stage  Register,  etc.  290 

114.  No.  633  Graphic  Water  Stage  Register,  etc.  293 

115.  No.  637  Long  Distance  Graphic  Water  Stage 

Register,     showing    the     Receiver     attach- 
ment     296 

116.  No.  638    Float    Operated    Sender,    for    Long 

Distance  Graphic  Register 299 

117.  No.  639  Long  Distance  Indicator  with  12  in. 

Dial    300 

118.  No.  639-A  Indicating  Gage   301 

119.  No.  9570  Precision  Balance 303 

120.  Packing   Box    309 


Gurley  Precise  Mountain  Transit 


TRANSITS 
CONSTRUCTION  OF  TRANSITS 

THE  TRANSIT  is  by  far  the  most  important  and 
indispensable  instrument  of  an  engineers'  outfit. 
With  it  the  engineer  can  read  and  lay  off  both 
horizontal  and  vertical  angles,  determine  a  level  line  or 
the  difference  in  elevation  between  two  points,  read  dis- 
tances by  means  of  the  stadia,  measure  grades  and 
distances  with  the  gradienter  and  determine  the  meridian 
by  the  compass,  by  direct  observation,  or  by  the  solar 
attachment. 

The  distinguishing  features  of  Gurley  Transits  as 
developed  after  many  years  of  study  and  experience, 
are  their  simplicity  of  construction,  ease  of  manipula- 
tion, and  accuracy  and  permanence  of  adjustments, 
which  are  all  made  without  undue  strain  on  any  part. 

The  essential  parts,  which  may  be  seen  in  the  illus- 
trations, and  in  section  in  Figure  1,  are  the  telescope 
with  its  axis,  the  standards,  the  circular  plates  with 
their  attachments,  the  sockets  upon  which  the  plates 
revolve,  the  leveling  head,  and  the  tripod  upon  which 
the  whole  instrument  stands. 

TELESCOPE.  The  different  parts  of  the  telescope 
are  shown  in  Fig.  1.  An  achromatic  lens  (H)  at  the 
enlarged  end  of  a  sliding  cylinder  mounted  near  each 
end,  in  bearings  (I)  of  hard  babbitt  metal,  is  moved  out 
or  in  to  bring  the  focus  of  the  rays  of  light  from  the 
object  viewed  to  an  inverted  image  in  the  plane  of  the 
cross  wires  (J)  to  be  there  magnified  by  an  eyepiece 
(T-W),  and  restored  to  its  natural  position. 


FIG.  1 

CROSS  SECTION  OF  TRANSIT 


TRANSIT  INSTRUMENTS  25 

The  telescope  is  secured  to  an  axis  having  multi- 
grooved  bearings  (F)  fitted  in  the  standards,  allowing 
the  telescope  to  transit  at  both  ends. 

The  various  sizes  of  telescopes,  made  to  suit  the 
instruments  on  which  they  are  to  be  used,  are  of  the 
best  quality.  They  must  be  free  from  chromatic  and 
spherical  aberration  and  of  as  high  a  magnifying  power 
as  is  consistent  with  good  illumination  and  sharp  defini- 
tion, or  resolving  power. 

The  lenses,  however  good,  must  be  so  accurately 
mounted  that  the  optical  axes  of  all  of  them  will  be  in 
one  straight  line.  This  imaginary  line,  called  the  line 
of  collimation  must  be  at  right  angles  to  the  axis  of 
revolution  for  all  positions  of  the  focusing  slide. 

OPTICAL  Axils.  The  intersection  of  the  cross  wires 
forms  a  point  which,  when  adjusted,  enables  the 
observer  to  fix  the  telescope  upon  an  object  with  pre- 
cision. The  process  of  bringing  the  intersection  of  the 
wires  into  the  optical  axis  is  called  the  adjustment  of 
the  line  of  collimation. 

One  of  the  babbitt  bearings  (I,  Fig.  1)  of  the  objec- 
tive slide  is  supported  in  a  ring  and  can  be  adjusted  with 
the  screws  (C  C). 

The  adjustment  of  the  objective  slide,  which  is 
described  on  pages  74  and  75,  keeps  the  line  of  collima- 
tion in  adjustment  through  the  whole  range  of  the  slide 
without  placing  any  strain  on  the  slide  or  bearings. 
This  adjustment,  which  is  one  of  the  distinctive  features 
of  Gurley  telescopes,  permits  the  alignment  of  both 
wires  with  equal  accuracy,  which  is  impossible  without 


26  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

it.  The  slide  adjustment  is  always  made  in  the  process 
of  manufacture,  and  needs  no  attention  from  the  engin- 
eer, unless  the  instrument  is  severely  injured. 

The  slides   are  now  made  to  focus  at  any  distance 
from  four  and  one-half  feet  to  infinity. 


FIG.  2 
No.   154  SHOWING  DUST  GUARD  FOR  OBJECTIVE 

DUST  GUARD  (No.  154)  for  the  objective  slide, 
is  placed  on  all  our  Transit  Telescopes.  A  velvet 
band  effectually  prevents  any  particle  of  dust  or  foreign 
substance  from  interfering  with  the  perfect  action  of 
the  slide.  It  also  helps  protect  the  objective  slide 
from  injury. 

CENTER  POINT.  To  facilitate  the  setting  of  the 
transit  precisely  under  a  given  point,  we  make  in  the  top 
of  the  ball  of  the  telescope  axis  and  directly  over  the 
center  of  the  instrument,  a  small  conical  hole  or  center 
point. 

EYEPIECE.  Four  lenses,  (T,  U,  R,  W,)  form  a 
compound  microscope  that  focuses  on  the  image  at  the 
cross  wires  and  conveys  the  magnified  image  to  the  eye, 
in  an  erect  or  natural  position.  Sometimes  an  eyepiece 


TRANSIT  INSTRUMENTS  27 

of  but  two  lenses  is  used.  While  this  absorbs  less  light 
and  therefore  gives  a  more  distinct  image,  it  presents  to 
the  eye  an  inverted  image  of  the  object  viewed. 
American  engineers  usually  prefer  the  erect  image. 

The  centering  of  the  eyepiece  is  effected  after  the 
wires  have  been  adjusted,  by  moving  the  ring  and  babbitt 
bearing  with  the  screws,  AA,  shown  on  the  outside  of 
the  tube,  until  the  intersection  of  the  wires  is  brought 
into  the  center  of  the  field  of  view. 

MAGNIFYING  POWER.  The  apparent  size  of  an 
object  viewed  through  the  telescope  is  as  many  times 
greater  than  the  image  which  the  naked  eye  sees,  as  the 
number  which  expresses  its  magnifying  power.  A  tele- 
scope which  magnifies  twenty  times,  increases  the 
visual  angle  in  this  same  proportion,  and  therefore 
diminishes  the  apparent  distance  of  the  object  to  one- 
twentieth  of  the  actual  distance.  In  other  words,  it  will 
show  an  object  two  hundred  feet  distant,  the  same  size 
as  if  it  were  only  ten  feet  from  the  naked  eye. 

It  is  often  supposed  that  the  greater  the  power  of  a 
telescope  the  better  it  is;  but  beyond  a  certain  limit, 
this  is  not  true.  As  only  a  given  amount  of  light  can 
enter  the  objective,  the  more  the  object  is  magnified  the 
less  clear  and  bright  will  it  appear.  A  power  of  from 
sixteen  to  twenty-six  diameters  in  the  telescopes  of 
transits  gives  the  best  results  for  regular  use. 


28 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


PLATINUM  CROSS 
WIRES.  The  cross 
wires  in  Gurley  tele- 
scopes are  filaments  of 
platinum,  mounted  on 
the  face  of  a  heavy 
brass  ring  which  will 
always  retain  its  shape. 
They  are  placed  at 
right  angles  with  each 
other,  so  as  to  divide 
the  field  of  view  into 

quadrants,  and  are  adjusted  in  the  line  of  collimation 
by  means  of  the  four  capstan  head  screws,  BB  and 
B'B',  Figure  3. 

For  special  cases  they  can  be  mounted  in  many 
other  forms. 

The  advantages  of  platinum  over  spider  web  have 
long  been  conceded.  It  is  smooth,  opaque  and  unaffected 
by  moisture.  The  desirability  of  non-transparent  wire 
is  manifested  when  sighting  against  the  sun  or  when 
observing  a  lamp  as  in  mine  wTork.  We  are  successfully 
drawing  wire  to  one  fifty-thousandth  of  an  inch  in  dia- 
meter. For  transits  we  use  wire  one  ten-thousandth  of 
an  inch  in  diameter,  selected  according  to  the  degree  it 
is  to  be  magnified. 

Unless  otherwise  specified  we  supply  fixed  stadia 
wires  with  most  of  our  instruments  as  they  are  preferred 
by  the  majority  of  engineers  because  they  cannot  be 
thrown  out  of  adjustment  accidentally. 


TRANSIT  INSTRUMENTS  29 

However,  when  requested,  we  will  substitute  adjust- 
able stadia  wires  which  are  necessary  if  the  user  wishes 
to  change  his  unit  of  measurement  from  feet  to  chains 
(1 :  100  -1 :  66).  In  all  cases  where  the  ratio  is  1 :  100  the 
interval  between  the  stadia  wires  need  not  be  changed 
as  the  ratio  1 :100  is  good  for  one  foot  to  one  hundred 
feet,  one  meter  to  one  hundred  meters  or  one  vara  to 
one  hundred  varas. 

DISAPPEARING  STADIA  WIRES.  The  Stadia  Wires 
are  usually  arranged  in  the  same  focal  plane  with  the 
cross  wires  so  that  they  may  be  seen  at  the  same  time. 
When  desired,  however,  they  may  be  placed  so  that  they 
are  out  of  focus  when  the  cross  wires  are  visible;  and 
conversely  when  the  stadia  wires  are  in  focus,  the  cross 
wires  are  invisible.  Some  engineers  like  this  method, 
but  it  has  the  disadvantage  that  changing  the  focus 
from  stadia  wires  to  cross  wires  or  vice  versa,  necessi^ 
tates  a  change  of  the  objective  focus.  For  this  reason, 
the  majority  of  engineers  prefer  the  regular  system; 
that  is,  with  all  the  wires  in  one  focal  plane.  This 
arrangement  of  the  wires  also  enables  them  to  observe, 
by  means  of  the  vertical  cross  wire,  whether  the  rod  is 
being  held  plumb. 

BEAMAN  STADIA  ARC.  The  Beaman  Stadia  Arc, 
described  on  page  90,  which  is  made  exclusively  by 
W.  &  L.  E.  Gurley,  avoids  the  use  of  all  stadia  compu- 
tations in  inclined  sights.  It  can  be  attached  to  any 
Gurley  transit  or  telescopic  alidade  having  a  vertical 
limb  four  inches  in  diameter  or  larger. 


30  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

THE  STANDARDS.  The  axis  on  which  the  telescope 
revolves,  or  transits,  is  supported  in  a  most  substantial 
manner.  The  original  design  of  the  standards  has  been 
much  improved  by  adopting  an  angular  section  and 
enlarging  the  bases  so  that  two  strong  screws  in  each 
base  may  firmly  secure  them  to  the  ribbed  plate.  Such 
standards  are  supplied  with  our  Light  Mountain  and 
Reconnoissance  Transits. 


FIG.  4 

ONE   PIECE   TRUSS   STANDARD 
PATENTED  JULY  25,  1916 

A  new  design  (patented),  as  here  shown,  was 
recently  introduced  by  us  and  represents  the  greatest 
advance  in  instrument  construction.  It  is  stronger  and 


TRANSIT  INSTRUMENTS  31 

more  rigid  than  any  other  form  of  standard.  Cast  of 
the  toughest  bronze,  in  one  piece,  and  with  angle  cross 
section,  it  provides  the  greatest  rigidity  with  the  least 
possible  weight.  The  principle  of  diagonal  cross  brac- 
ing is  used  here  and  the  supporting  members  are  carried 
as  far  up  on  the  legs  as  is  possible  without  interfering 
with  the  use  of  the  instrument.  The  base  is  wide,  and 
its  attachment  to  the  top  plate  by  eight  large  screws 
allowrs  the  development  of  the  full  strength  of  the  deeply 
ribbed  plate  for  support  and  reinforcement,  making  the 
whole  structure  mechanically  one  piece  for  withstand- 
ing stress.  The  finish  of  the  standard  is  a  beautiful 
and  very  durable  morocco,  applied  directly  to  the  surface 
of  the  casting,  which  thus  retains  its  skin  intact.  The 
internal  stresses  of  the  metal  are  relieved  by  a  process 
of  artificial  aging  in  which  the  metal  assumes  its  perma- 
nent set  without  any  loss  of  its  tenacity  or  rigidity.  The 
bearings  for  the  axis  are  of  perfect  circles  in  cross- 
section,  but  instead  of  being  plain  cylinders,  they  have 
V  threads  of  zero  lead.  They  are  always  ground  into 
place  to  insure  a  perfect  fit.  This  form  of  ground 
multi-shoulders,  as  illustrated  at  F,  Fig.  1,  adds  rigidity 
to  the  standards  and  automatically  prevents  any  loose- 
ness or  lateral  motion,  regardless  of  any  possible  wear 
through  long  use. 

On  the  right  hand  bearing  of  the  standard  there  is 
an  adjustable  block  whereby  the  axis  may  be  made 
truly  horizontal  or  at  right  angles  to  the  vertical 
spindle. 

THE  Axis  CLAMP  AND  TANGENT,  which  is  regularly 
supplied  on  all  transits,  consists  of  an  arm,  K,  Fig.  1, 


32 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


one  end  of  which  encircles  the  telescope  axis,  and  can 
be  clamped  to  it.  The  other  end  is  held  between  the 
tangent  screw  on  one  side  and  the  tangent  slide  and 
spring  on  the  other.  These  are  supported  from  the 
standards.  When  clamped  the  telescope  may  be  tilted 
slowly  by  means  of  the  tangent  screw ;  when  undamped, 
it  may  be  revolved  freely  in  either  direction. 


FIG.  5 

RADIALLY  RIBBED  AND  DISHED  LIMB  AND  PLATE, 
AND  TAPERED  CENTERS 

THE  MAIN  PLATE.  By  a  system  of  deep  ribbing, 
the  top  plate  has  been  materially  stiffened  without  add- 
ing to  its  weight,  and  the  liability  of  warping  with  age 
has  been  reduced.  It  carries  the  standards  supporting 
the  telescope,  the  compass  box  with  its  movement  for 
magnetic  declination,  the  verniers  for  the  horizontal 
limb,  two  levels  at  right  angles  to  each  other,  and  the 
support  for  the  tangent  screw  for  movement  about  the 
vertical  axis.  Note  Fig.  10  that  the  longitudinal  plate 


TRANSIT  INSTRUMENTS 


33 


level  is  of  extra  length,  providing  a  more  precise  check 
when  measuring  vertical  angles  than  is  possible  with  a 
short  level. 


FIG.  6 
TOP  PLATE  OF  THE  LIGHT  MOUNTAIN  TRANSIT, 

SHOWING   LOCATION    OF   VERNIERS,    LEVELS,  VARIATION 
ARC     PINION,     AND     NEEDLE     LIFTER    SCREW 

THE  COMPASS  CIRCLE  is  silvered,  graduated  and 
figured  0  to  90  each  way.  The  graduations  of  this 
circle,  on  Transits  Nos.  6-A  to  18-A,  are  half  degrees 
and  the  declination  arc  reads  bv  vernier  to  one  minute. 


34  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

On  Transits  Nos.  25-A  to  32-A  the  compass  circle  is 
graduated  to  whole  degrees  and  the  declination  arc 
reads  by  vernier  to  five  minutes.  The  declination  arcs 
are  movable  by  a  pinion. 

THE  COMPASS  Box  containing  the  needle  is  covered 
by  a  glass  to  exclude  moisture  and  air.  These  covers 
on  all  Gurley  transits  are  made  of  specially  selected  plate 
glass,  beveled  on  the  edge  and  set  flush  with  the  bezel 
ring,  thus  facilitating  the  removal  of  moisture  from  the 
top  of  the  glass  and  affording  an  unobstructed  observa- 
tion of  the  compass  face. 

THE  MAGNETIC  NEEDLE,  made  of  special  magnet 
steel,  has  a  cap  in  which  is  inserted  a  polished  jewel 
center  and  this,  resting  upon  the  hardened  and  polished 
point  of  the  center  pin,  allows  the  needle  to  play  freely 
and  settle  in  the  magnetic  meridian. 

The  needle  has  on  its  South  end  (North  end  for 
Southern  hemisphere)  a  coil  of  wire,  easily  moved  to 
adjust  the  balance  of  the  needle  against  dipping.  The 
needles  are  balanced  as  nearly  as  possible  for  the  loca- 
tion to  which  they  are  to  be  shipped,  so  that  only  a 
slight  adjustment  should  be  necessary.  A  screw  passing 
through  the  upper  plate  moves  a  concealed  lever  by 
which  the  needle  button  is  raised  against  the  setting, 
thus  lifting  the  needle  from  the  pin  so  as  to  check  its 
vibration,  or  to  hold  it  up  against  the  glass  when  not  in 
use,  avoiding  unnecessary  wear  of  the  jewel  center  and 
the  pivot. 

The  test  of  the  delicacy  of  a  magnetic  needle  is  the 
number  of  horizontal  vibrations  which  it  will  make  in  a 


TRANSIT  INSTRUMENTS  35 

certain  arc  before  coming  to  rest.  Most  surveyors 
desire  also  a  quivering  motion  in  the  needle.  This 
quality,  which  is  manifested  more  in  a  horizontal  than 
in  a  vertical  needle,  depends  upon  the  close  coincidence 
of  the  point  of  suspension  with  the  center  of  gravity  of 
the  needle,  and  merely  serves  to  show  that  the  cap  is 
unobstructed. 

PLATE  LEVELS.  The  two  plate  levels,  mounted  on 
brass  posts  or  studs,  are  at  right  angles  to  each  other 
so  as  to  level  the  plate  in  all  directions.  The 
position  of  the  levels,  near  the  edge  of  the  plate, 
makes  them  accessible  for  adjustment  and  permits  the 
use  of  longer  and  consequently  more  accurate  levels 
than  if  placed  inside  the  compass  box.  These  levels 
are  held  firmly  in  place  by  the  capstan  nuts  above  and 
below  each  end.  They  cannot  possibly  be  jarred  out 
of  position.  Their  adjustment  is  made  by  turning  the 
capstan  head  nuts  at  either  end.  The  glass  vials  used 
in  the  levels  of  all  Gurley  transits  are  ground  on  their 
inner  surface  to  give  the  bubble  an  even  motion  and  the 
required  degree  of  sensitiveness. 

HORIZONTAL  LIMB.  All  cast  metal  parts,  but 
more  particularly  the  casting  of  the  limbs,  should  be 
thoroughly  aged.  A  fresh  casting  will  shrink  and  warp 
like  a  piece  of  wood,  but,  of  course,  to  a  lesser  degree. 

We  machine  the  limbs,  apply  the  sterling  silver,  and 
then  completely  season  them  before  putting  them 
through  the  final  operations  of  finishing  and  graduating. 
To  secure  the  utmost  accuracy  and  to  avoid  any  possi- 
bility of  molecular  changes,  the  limbs  are  finished  and 
the  figures  engraved  before  the  graduating  is  done, 


36 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


which  is  the  last  process  before  they  are  placed  in  their 
respective  instruments. 

The  form  of  the  limb  has  been  considerably  changed 
by  a  greater  dishing,  which  adds  to  the  rigidity  and 
allows  deeper  ribbing. 


88 

I 

. 

til 


&  L.  E.  Gurley 
Troy,   N.  Y. 


Limb  I. 


The  figures  are  in  two  rows, 
in  quadrants  from  0  to  90 
each  way  inner  row,  and 
from  0  to  360  outer  row. 


FIG.  7 

The  graduations,  cut  on  sterling  silver,  are  usually 
to  half  degrees,  reading  by  vernier  to  one  minute.  If 
desired,  they  may  be  cut  to  thirds,  quarters  or  sixths  of 


TRANSIT  INSTRUMENTS 


37 


a  degree,  with  verniers  reading  to  thirty,  twenty,  fifteen 
or  ten  seconds,  but  at  an  additional  cost.  This  is 
known  as  the  sexagesimal  system. 

If  desired,  one  or  both  verniers  may  be  graduated 
to  read  to  one-hundredth  or  one-fiftieth    of    a    degree. 


W.   &  L.  E.  Gurley 
Troy,   N.  Y. 


The  figures  arein  two  rows, 
each  row  from  0  to  360, 
but  reading  in  opposite 
directions,  and  inclined 
in  the  direction  in  which 
they  increase. 


FlG.    8 


Another  form  is  to  graduate  the  limb  to  one  hundred 
grads  to  the  quadrant,  the  vernier  reading  to  one  one- 
hundredth  of  a  grad.  This  is  called  the  centesimal 
svstem. 


38  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

In  artillery  practice,  the  mil  is  used  because  of  its 
convenience  in  the  rapid  calculation  of  small  angles  in 
fire  control.  For  this  purpose  the  mil  is  taken  to  be 
1/6400  of  a  circumference. 

LIMB  FIGURING.  Various  methods  of  figuring  are 
employed.  The  two  forms  most  commonly  used  are 
shown  on  pages  36  and  37.  Limb  I  has  two  rows,  the 
inner  row  figured  in  quadrants  as  a  compass  circle  and 
the  outer  row  from  0  continuous  to  360°,  reading  clock- 
wise. Limb  IV  has  two  rows  of  figures,  each  0  to  360, 
but  in  opposite  directions  and  inclined  in  the  direction 
of  increase. 

THE  VERNIERS.  As  shown  at  V  in  the  sectional  cut, 
Fig.  1,  the  horizontal  verniers  are  attached  to  the  main 
plates  and  revolve  within  the  horizontal  limb,  with  their 
surfaces  flush  and  so  close  that  there  is  no  apparent 
parallax.  They  are  placed  thirty  degrees  to  the  left  of 
the  line  of  sight  and  can  be  easily  read  without  change 
of  position  by  the  observer.  They  are  covered  with 
selected  plate  glass  carefully  cemented  to  exclude 
moisture  and  dust.  The  upper  surface  of  the  glass  is 
flush  with  the  plate,  thus  they  are  easy  to  clean  and 
there  are  no  frames  or  rims  to  cast  shadows  or  col- 
lect dust. 

The  use  of  two  opposite  verniers  give  the  means  of 
cross  checking  the  graduations  and  the  perfection  with 
which  they  are  centered.  Thus  the  accuracy  of  the  angle 
readings  is  indicated. 

ONE  GRADUATION  is  ADDED  to  each  end  of  the  vernier 
to  enable  the  last  numbered  division  to  be  more  easily 


TRANSIT  INSTRUMENTS  39 

read  but  this  has  only  the  practical  use  indicated  and  is 
not  considered  in  calculating  the  smallest  reading  of  the 
vernier.  With  the  exception  of  the  extra  graduation 
mentioned  above,  the  number  of  spaces  on  the  vernier 
at  one  side  of  the  zero  graduation  is  equal  to  the  number 
of  parts  into  which  the  smallest  division  on  the  limb  is 
to  be  divided. 

To     FIND     THE     SMALLEST    READING     OF     THE     VERNIER, 

divide  the  value  of  the  smallest  space  on  the  limb  by 
the  number  of  parts  into  which  this  space  is  to  be 
divided,  the  resulting  quotient  is  the  smallest  reading 
of  the  vernier.  Thus  in  Fig.  9  we  have  a  vertical 
limb  graduated  into  half  degrees  or  thirty  minute  spaces, 
the  vernier  is  shown  between  the  standard  legs  and  is 
divided  into  thirty  parts  either  side  of  the  zero;  the 
vernier  therefore  reads  to  one  thirtieth  of  a  graduation 
or  a  single  minute. 

To   READ    THE    TRANSIT   VERNIER.        Note   the    position 

of  the  zero  on  the  limb  and  read  to  the  nearest  whole 
space  the  position  of  the  zero  of  the  vernier  with  respect 
to  it.  Reading  in  the  direction  of  increasing  limb 
figures,  count  the  graduations  on  the  vernier  from  zero 
to  the  one  which  coincides  with  a  graduation  on  the 
limb.  The  sum  of  these  two  readings  will  be  the  read- 
ing required. 

Divisions  should  be  counted  in  the  direction  of  in- 
creasing limb  figures. 

For  example,  in  Fig.  9,  the  vernier  zero  reads  be- 
tween 5°  and  5%*.  Counting  the  vernier  divisions  to 
the  left,  it  is  seen  that  the  16th  line  coincides  with  a 
line  of  the  arc.  The  correct  reading  is  therefore  5°  16', 


40  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Had  the  vernier  zero  read  between  5%°  and  6°,  the 
vernier  reading  would  have  been  added  to  5 1/2°  and  the 
result  would  have  been  5°  46'. 

REFLECTORS.  Reflectors  of  white  opaque  celluloid, 
or  of  glass  if  preferred,  are  placed  back  of  the  horizontal 
verniers  to  reflect  a  white  light  and  to  eliminate  glare. 


FIG.  9 
No.  149  BEAMAN  STADIA  ARC, 

ATTACHED  TO  THE  VERTICAL  ARC  OF  A  TRANSIT 


TRANSIT  INSTRUMENTS  4-1 

THE  LIMB  CLAMP  AND  TANGENT.  The  tangent 
hanger,  fastened  to  the  edge  of  the  main  plate,  carries 
the  tangent  screw  and  nut  on  one  side,  and  opposed  to 
them  the  tangent  spring,  slide,  and  barrel.  The  spring 
is  made  large  enough  to  give  practically  the  same  force 
throughout  the  length  of  its  travel. 

The  limb  clamp,  D,  Fig,  1,  is  a  heavy  ring  and 
arm  which  is  fitted  on  the  socket  so  as  to  turn  freely. 
The  clamp  screw,  E,  pushing  against  a  plunger,  operates 
to  clamp  the  ring  firmly  around  the  socket  without  tend- 
ing to  turn  it.  The  arm  of  the  clamp  is  held  between 
the  tangent  screw  and  spring. 

When  the  clamp  screw,  E,  is  loosened,  the  plate  may 
be  freely  turned  to  any  desired  position  for  setting  the 
verniers  or  sighting  the  telescope.  When  the  clamp 
screw  is  turned  lightly  against  the  plunger,  the  plate  is 
held  firmly  in  position  with  reference  to  the  limb ;  and 
it  may  be  given  a  very  slow  motion  by  turning  the  tan- 
gent screw. 

Because  of  the  special  form  of  Gurley  clamps,  only 
a  very  light  pressure  of  the  clamp  screw  is  necessary  to 
make  them  hold.  The  heads  of  the  clamp  screws  are 
therefore  made  small  to  prevent  unnecessary  force  being 
applied  to  the  screw  and  clamp. 

THE  SOCKETS.  The  sockets  are  compound.  The 
interior  spindle  Y,  Fig.  1,  attached  to  the  main  plate  — 
carrying  it  and  its  attachments  —  turns  in  the  inter- 
mediate socket  S  to  which  the  limb  is  attached.  When 
clamped,  this  socket  turns  in  the  socket  of  the  leveling 
head,  governed  by  a  second  clamp  and  tangent  movement 
with  opposing  spring. 


42  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  sockets  or  centers  are  constructed  with  the 
greatest  care,  are  of  carefully  chosen  composition  and 
are  made  of  different  degrees  of  hardness  to  eliminate 
friction  and  wear.  They  are  truly  concentric,  are  of 
substantial  diameter  and  length  and  are  designed  to  pro- 
vide maximum  stability  in  the  most  vital  parts  of  the 
instrument. 

THE  LEVELING  HEAD.  The  outer  socket  has  four 
ribbed  arms  that  bear  the  nuts  for  the  leveling  screws. 
At  its  lower  end  there  is  a  hemispherical  nut  fitting  in 
a  corresponding  cup  in  the  shifting  center,  which  is  the 
center  of  movement  when  leveling.  The  leveling  screws 
are  nicely  fitted  with  long  bearings  in  the  nuts  and  are 
protected  from  dust  by  covers.  The  lower  ends  of  the 
screws  rest  in  cup  bearings  fitted  with  fiber  bushings  to 
eliminate  friction.  The  cups  avoid  marring  the  plate 
when  shifting  the  instrument  from  side  to  side  on  the 
tripod.  To  prevent  cramping,  the  centers  of  the  lower 
ends  of  the  leveling  screws  are  in  line  with  the  center 
of  the  hemispherical  nut,  even  when  the  leveling  head 
is  tilted  far  to  one  side. 

SHIFTING  CENTER.  The  base  plate  is  in  two  parts. 
The  outer  part  is  threaded  to  screw  on  the  metal  head 
of  the  tripod  and  the  inner  part  encircles  the  hemis- 
pherical nut  of-  the  leveling  head.  When  the  leveling 
screws  are  loosened  the  whole  instrument  can  be  moved 
so  that  the  plummet  may  be  precisely  suspended  over  a 
desired  point.  The  action  of  the  leveling  screws  on  the 
base  plate  as  the  instrument  is  leveled  serves  as  a  clamp, 
thus  preventing  any  inadvertant  shift  after  it  is  once  set. 


TRANSIT  INSTRUMENTS  43 

THE  TRIPOD.  The  tripod  has  a  head  of  bronze  with 
three  strong  tenons  to  receive  the  wooden  legs,  the 
upper  ends  of  which  are  pressed  firmly  on  each  side  of 
the  tenon  by  a  bolt  and  wing  nut,  which  can  be  tightened 
by  hand  and  thus  kept  firm.  The  lower  end  of  each 
leg  has  a  metal  shoe  with  hardened  point,  securely 
fastened  to  the  wood.  There  are  four  styles  of  legs  — 
the  solid  round  leg,  the  split  leg,  the  extension  leg  and 
jointed  extension  leg. 

For    illustrations    and    descriptions    see    pages    238 
to    242. 


INVITATION   TO  VISIT   OUR   FACTORY 

The  extent  of  our  business  makes  it  impracticable 
for  us  to  personally  interview  but  a  small  number  of 
our  customers;  therefore,  we  extend  a  cordial  invitation 
to  all  of  our  friends  to  call  on  us  whenever  it  is  conven- 
ient to  do  so.  It  is  our  desire  to  become  better 
acquainted  and  to  more  fully  express  our  appreciation 
of  the  co-operation  and  good  will  which  have  so  largely 
contributed  to  the  success  of  our  efforts. 


44  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


DISTINCTIVE   FEATURES   OF   GURLEY   TRANSITS 


Carley 


FIG.   10 
No.  27-A  PRECISE  TRANSIT 


TRANSIT  INSTRUMENTS  45 


SELECTION  OF  TRANSITS 

VARIETY  OF  MODELS.     As  we  make  various  models  and 
sizes,  it  is  possible  to  select  an  instrument  which 
will  suit  every  individual  requirement.     The  differ- 
ence in  prices  does  not  indicate  a  difference  in  quality,  as 
we  make  only  one  grade.   The  price  is  based  on  the  actual 
cost  of  manufacture  and,  in  each  instance,  it  is  the  lowest 
for  which  a  high  grade  and  fully  warranted  instrument 
can  be  made. 

THE  GURLEY  PRECISE  TRANSITS  with  patented  One 
Piece  Truss  Standard  and  other  new  features  represent 
the  last  word  in  design  and  construction  and,  as  their 
name  implies,  they  are  adapted  for  work  which  demands 
the  highest  degree  of  accuracy  and  refinement. 

They  are  made  in  four  sizes;  the  largest  size  is 
No.  18-A,  Hell  Gate  Model;  medium  size,  Nos.  6-A  to 
10-A  and  10-A-3;  the  Light  Mountain  size,  Nos.  25-A 
to  32-A;  and  the  Explorers  size,  Nos.  20-A  to  24-A. 


46  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


HELL  GATE  BRIDGE  ERECTION  CONTROLLED  BY 
A  GURLEY  PRECISE  TRANSIT 

THE  BRIDGE  OF  THE  NEW  YORK  CONNECTING  RAIL- 
ROAD over  the  East  River  at  Hell  Gate  stands  as  one 
of  the  most  notable  achievements  in  bridge  engineering 
in  recent  years.  It  is  a  steel  arch  of  970  feet  span  and 
carries  four  tracks. 

The  rapid  tidal  currents  of  the  river  and  the  neces- 
sity of  maintaining  a  free  passage  for  navigation  during 
the  construction  made  the  use  of  false  work  impossible. 
The  arch  was  built  from  the  two  abutments  simultan- 
eously and  its  successful  completion  demanded  that  the 
ends  of  the  two  halves  should  meet  in  mid-stream  with 
extreme  exactness.  This  necessitated  instrument  con- 
trol of  the  very  highest  precision. 

The  engineers  who  had  this  work  in  charge  selected 
a  Gurley  Precise  Transit  and  staked  their  engineering 
reputation  on  this  choice.  Their  confidence  in  the 
instrument  was  justified  when  the  cantilever  members 
met  within  one-quarter  of  an  inch  of  their  predetermined 
position. 

Long  base  lines  lateral  to  the  structure  were  laid  out 
on  both  shores.  Concrete  piers  were  built  at  the  tri- 
angulation  points,  each  pier  having  a  permanent  base 
for  the  Gurley  Precise  Transit  which  governed  the 
work. 

Vertical  and  horizontal  angles  to  10  seconds  were 
taken  to  panel  points  as  erection  proceeded,  the  exact 


TRANSIT  INSTRUMENTS 


FIG.  11 
No.   10-A  PRECISE  TRANSIT 


48  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

position  of  each  point  being  accurately  determined  and 
checked  bv  observations  from  several  stations. 


FIG.   12 
VIEW   OF    HELL   GATE    BRIDGE    DURING    CONSTRUCTION 


TRANSIT  INSTRUMENTS 


FIG.   13 
No.  18-A  PRECISE  TRANSIT,  HELL  GATE  MODEL 


50  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

PRECISE  TRANSIT,  HELL  GATE  MODEL 

This  transit  is  of  the  Gurley  One  Piece  Truss 
Standard  construction  and  represents  our  supreme 
efforts.  It  is  the  result  of  seventy-five  years  experience 
in  designing  and  building  engineering  instruments.  It 
embodies  all  of  the  desirable  qualities  of  our  regular 
model  Precise  Transits  and  has  the  added  advantages  of 
the  special  features  as  shown  in  Fig.  13. 

Thus  it  is  adapted  for  triangulation,  bridge  building, 
municipal  engineering,  etc.,  and  for  all  classes  of  work 
demanding  the  highest  degree  of  accuracy  and  refine- 
ment. 

Both  the  horizontal  and  the  vertical  limbs  are  grad- 
uated to  10  minutes  and  each  reads  by  two  opposite 
double  verniers  to  10  seconds.  A  rigid  frame  or  guard 
protects  the  vertical  circle  and  supports  a  long  sensitive 
level  which  controls  the  zeros  of  the  double  opposite 
verniers,  also  supported  by  the  frame.  Microscopes 
suspended  over  each  vernier  facilitates  the  reading  of 
the  fine  graduations.  The  telescope  has  an  inverting 
eyepiece. 

MEDIUM  SIZE  PRECISE  TRANSITS 

Transits  with  a  6.25"  horizontal  limb  are  listed  as 
Nos.  6-A,  7- A,  8-A,  9-A,  10-A  and  10-A-3,  the  numbers 
indicating  different  combinations  of  attachments,  such 
as  level  on  telescope,  vertical  circle  or  arc,  and  gradien- 
ter.  The  limb  is  graduated  on  sterling  silver  and  reads 
by  two  opposite  double  verniers  to  single  minutes.  Finer 
graduations  can  be  supplied  at  additional  cost. 


TRANSIT  INSTRUMENTS  51 

The  telescope  is  eleven  inches  long,  erecting,  and 
has  a  power  of  26  diameters.  The  compass  needle  is 
3^/2  inches  long  and  has  an  arc  for  setting  off  the  mag- 
netic declination.  The  instruments,  without  tripod, 
weigh  from  15.5  to  16.5  pounds. 

Numbers  25-A,  26-A,  27-A,  28-A,  29-A,  30-A  and 
32-A  apply  to  transits  having  a  5.65"  horizontal  limb. 
The  telescopes  have  erecting  eyepieces,  a  power  of  20 
diameters  and  are  supported  by  our  new  One  Piece 
Truss  Standard.  They  are  equipped  with  a  three  inch 
needle  and  weigh  but  eleven  to  thirteen  pounds. 

Transits  Nos.  25,  26,  27,  28,  29  and  30  also  have  a 
5.65"  horizontal  limb.  They  are  like  Nos.  25-A  to  32-A 
except  that  the  telescope  is  supported  by  two  separate 
standards  and  the  compass  needle  is  four  inches  long. 

Detailed  specifications  of  all  transits  are  given  in  a 
bulletin  in  the  back  of  this  Manual. 


52  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

THE  GURLEY  THREE  SCREW  LEVELING  HEAD,  as 
shown  in  Fig.  14,  is  of  a  design  which  gives  the  utmost 
rigidity  without  being  cumbersome  and  provides  a  shift- 
ing center  of  liberal  movement. 

Spiral  springs  are  not  used  in  the  construction  of 
this  head  which  can  be  immovably  clamped  before  angle 
reading  is  started.  Our  instrument  need  not  be  de- 
tached from  the  tripod  when  being  carried  between 
stations. 

The  three  screw  leveling  head  is  made  only  to  order. 
It  can  be  furnished  with  any  RCWT  Gurley  Transit,  if 
desired,  at  an  extra  cost. 


TRANSIT  INSTRUMENTS 


53 


FIG.   14 
No.  10-A-3  PRECISE  TRANSIT 

WITH  THREE-SCREW  LEVELING  HEAD 


54  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


LIGHT  MOUNTAIN  TRANSITS 

THE  GURLEY  LIGHT  MOUNTAIN  TRANSIT.  Its  high 
grade  construction  and  light  weight  have  made  this  the 
most  popular  Gurley  Transit,  and  in  fact  it  is  the  ideal 
transit  for  all-around  work.  Although  especially 
adapted  for  Mine  and  Mountain  Surveys,  it  is  used  for 
Municipal,  Highway  and  Railway  Engineering  as  well 
as  for  Bridge  and  General  Construction,  Solar  Observa- 
tions and  Forest  Surveys.  It  is  the  best  knorvn  transit 
in  America  and  we  stake  our  reputation  on  the  results 
obtained  from  its  use.  It  can  be  improved  only  by 
substituting  in  place  of  the  two  separate  standards,  our 
patented  ONE  PIECE  TRUSS  STANDARD. 


TRANSIT  INSTRUMENTS 


55 


FIG.   15 

No.  28  LIGHT  MOUNTAIN  TRANSIT 
The  Best  Known  Transit  in  America 


56  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

THE  GURLEY  EXPLORERS  PRECISE  TRANSIT.  This  is 
the  smallest  and  lightest  Gurley  transit  but  it  is  equal 
in  quality  and  similar  in  construction  to  our  Precise 
Light  Mountain  Transit  and  therefore  can  be  used  for 
work  of  a  high  degree  of  accuracy. 

As  its  name  implies,  it  is  designed  for  engineers 
working  in  a  new  or  undeveloped  country  and  also  for 
those  whose  work  is  scattered  and  who  are  obliged  to 
travel  constantly.  It  is  also  used  with  great  success  by 
Mining  Engineers  who  prefer  or  require  a  smaller  and 
lighter  instrument  than  the  Light  Mountain  pattern. 
When  placed  in  its  leather-covered  case  it  can  be  packed 
in  a  twenty-four  inch  dress  suit  case,  together  with  its 
special  jointed  extension  tripod.  An  Explorers  Level, 
described  on  page  196,  and  an  Explorers  Alidade, 
described  on  page  249,  can  be  included,  in  the  suitcase, 
if  desired. 


TRANSIT  INSTRUMENTS 


57 


EXPLORERS  PRECISE  TRANSIT 


FIG.   16 

No.  20-A  EXPLORERS  PRECISE  TRANSIT 
The  smallest  and  lightest  Gurley  Transit 


58 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


'- 


FIG.   17 

EXPLORERS  TRANSIT  WITH  ITS  SPECIAL  JOINTED 

EXTENSION  TRIPOD,  CANVAS  CARRYING  CASE,  AND 

LEATHER  COVERED   WOODEN  BOX 


TRANSIT  INSTRUMENTS 


59 


FIG.  18 

EXPLORERS  TRANSIT,  WITH  ITS  SPECIAL  TRIPOD, 
PACKED  IN  A  DRESS  SUIT   CASE   24   INCHES   LONG 


60  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

RECONNOISSANCE  TRANSIT 

The  Gurley  Reconnoissance  Transit  meets  the  de- 
mand for  a  very  light  instrument  for  rapid  work. 
Constructed  like  our  Mountain  Transits,  with  long  cen- 
ters and  with  ribbed  leveling  head,,  limb  and  main  plate, 
and  made  with  the  same  care  as  our  larger  and  more 
expensive  patterns,  it  is  recommended  as  reliable  for  a 
great  variety  of  work. 

Its  accuracy,  its  convenience  in  carrying,  and  its 
proved  ability  to  stand  up  satisfactorily  under  severe 
use,  have  made  this  transit  especially  popular  with  Sur- 
veyors, Contractors,  Road  Engineers,  Architects  and 
Builders. 


TRANSIT  INSTRUMENTS 


61 


FIG.  19 
No.  102  RECONNOISSANCE  TRANSIT 


62  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

CARE  OF  THE  TRANSIT 

TOO  much  emphasis  cannot  be  laid  upon  the  impor- 
tance of  care  in  handling  and  transporting  instru- 
ments of  precision.  Every  instrument  as  it  leaves 
our  factory  is  properly  lubricated  and  adjusted  ready 
for  use.  It  will  remain  so  for  a  long  time,  if  treated 
as  an  instrument  of  precision. 

HANDLING  THE  INSTRUMENT.  Extreme  care  must  be 
taken  at  all  times  to  prevent  the  instrument  from  receiv- 
ing shocks  which  may  throw  it  out  of  adjustment.  When 
shipped  for  any  distance  the  instrument  case  should  be 
enclosed  in  an  outer  packing  box  and  carefully  sur- 
rounded with  some  shock  absorbing  material.  If  any- 
thing dusty,  as  excelsior,  is  used,  the  case  should  first 
be  wrapped  in  paper  with  the  edges  pasted  to  keep  out 
the  dirt.  When  not  in  use,  the  instrument  should  be 
placed  in  its  case.  When  carrying  the  instrument 
mounted  on  the  tripod,  through  brush,  or  through  doors 
of  a  building  or  similar  places,  the  tripod  should  be 
carried  under  the  arm  and  not  over  the  shoulder,  thus 
avoiding  the  possibility  of  accidently  striking  the  instru- 
ment. When  setting  up  the  instrument,  the  tripod 
should  not  be  set  too  high,  as  it  may  be  easily  tipped 
over.  Particular  care  should  be  given  to  this  feature 
when  setting  the  tripod  on  steps  or  on  a  hillside  where 
one  leg  is  generally  shortened  and  placed  at  a  high 
angle. 

In  handling  the  instrument,  care  should  be  taken  to 
grip  it  at  such  points  that  no  strain  will  be  put  on  any 
of  the  adjustments.  The  Gurley  method  of  packing 


TRANSIT  INSTRUMENTS  63 

transits  prevents  any  lateral  strain  from  being  placed 
upon  the  spindle,  sockets,  or  standards.  To  remove 
the  transit  from  the  box,  first  lift  out  the  packing  pieces 
from  the  ends  of  the  telescope  axis,  grasp  the  tops  of 
the  standards  with  both  hands,  or  the  telescope  axis 
with  one  hand,  and  lift  the  instrument  out  of  the  box. 
To  place  upon  the  tripod,  unscrew  the  leveling  fcead 
clamp,  lift  the  instrument  and  with  the  fingers  under 
the  limb  or  body  and  the  thumbs  on  the  top  plate,  set 
upon  the  tripod.  Retain  the  grasp  with  one  hand  and 
with  the  other,  screw  the  bottom  plate  on  the  tripod 
head. 

The  transit  may  also  be  lifted  from  the  box  by  turn- 
ing the  telescope  to  a  vertical  position,  reaching  down 
into  the  box  and  grasping  it  under  the  limb  as  described 
above.  This  method  has  the  advantage  that  the  transit 
may  be  placed  directly  upon  the  tripod  without  chang- 
ing the  hands.  It  should  never  be  lifted  by  taking 
hold  of  the  standards  except  as  described  above,  nor 
should  it  be  lifted  or  carried  by  means  of  the  leveling 
head,  leveling  screws  or  bottom  plate,  when  not  on  the 
tripod,  without  being  steadied  near  the  top. 

Before  attempting  to  turn  the  transit  in  either  of 
the  sockets,  be  sure  that  at  least  one  of  the  clamp  screws 
has  been  loosened.  Turn  the  transit  by  means  of  the 
lower  part  of  the  standards,  the  plate  or  the  tangent 
attachments,  but  not  by  the  telescope. 

In  tightening  clamp  screws  it  is  necessary  only  to 
screw  them  home  lightly,  as  the  design  of  Gurley  clamps 
makes  them  grip  very  firmly.  If  too  much  force  is 


64  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

applied  to  the  clamp  screw,  the  thread  will  be  strained 
and  worn  unnecessarily. 

All  bearing  surfaces  are  made  as  nearly  frictionless 
as  possible  and  therefore  need  very  little  lubrication. 
If  it  does  become  necessary  to  lubricate  a  thread  or 
bearing,  only  the  best  grade  of  watch  oil  should  be  used 
and  only  a  very  small  amount  of  that.  A  thin  film  of 
light  oil  is  all  that  most  of  the  fitted  surfaces  will  admit. 
Oil  should  be  carefully  wiped  from  exposed  parts,  as  it 
will  cause  dust  to  adhere. 

CLEANING  THE  INSTRUMENT.  So  far  as  possible,  all 
outside  cleaning  or  dusting  of  instruments  should  be 
done  with  a  soft  camel  hair  brush.  Care  should  be 
taken  not  to  rub  the  lacquer  from  the  finished  surfaces, 
as  the  exposed  metal  will  readily  tarnish.  Alcohol, 
or  similar  solvents  should  never  be  used  on  the  instru- 
ments. 

In  cleaning  the  lenses,  first  remove  the  dust  with  a 
soft  brush  and  then  wipe  lightly  with  a  soft,  dry  cloth, 
free  from  lint.  Rubbing  the  lenses  dry  sometimes 
causes  small  particles  to  stick  to  them,  and,  in  this  case, 
blowing  the  breath  on  the  glass  will  furnish  sufficient 
moisture  so  that  they  may  be  rubbed  off  easily.  If  any 
liquid  is  brought  into  contact  with  the  lenses,  it  is  liable 
to  penetrate  the  mounting  and  give  bad  results. 

Do  not  rub  the  silver  upon  which  the  graduations  are 
cut,  as  this  will  make  bright  spots,  which  cause  difficult 
reading. 

Particular  care  must  be  taken  to  prevent  anything 
from  coming  into  contact  with  the  graduated  edge,  not 


TRANSIT  INSTRUMENTS  65 

even  rubbing  this  with  a  soft  cloth.  As  this  is  solid 
silver,  it  is  soft  and  easily  damaged.  If  necessary  to 
clean  the  limb,  dampen  a  soft  cloth,  dip  it  in  powdered 
charcoal,  and  rub  lightly  over  the  silver,  being  careful 
not  to  rub  over  the  graduated  edge. 

DISMOUNTING  THE  INSTRUMENT.  In  case  of  damage 
to  the  instrument,  it  should,  if  possible,  be  returned  to 
the  maker  for  repairs.  If  absolutely  necessary,  how- 
ever, to  take  the  instrument  apart,  it  should  be  done  in 
some  place  which  is  free  from  dust;  never  out  in  the 
open  where  dirt  may  be  blown  into  the  working  parts 
as  they  are  being  assembled. 

REMOVING  THE  OBJECTIVE  LENS.  Unscrew  the  dust 
guard  on  the  end  of  the  main  tube  and  then  unscrew  the 
small  ring  in  the  end  of  the  slide  head.  This  brings 
with  it  the  complete  lens  in  its  setting.  The  objective 
consists  of  two  lenses  held  together  by  two  metal  rings. 
The  former  are  marked  on  the  edge  with  a  cross  so  that 
they  may  be  put  back  together  in  the  same  relative  posi- 
tion. It  is  always  necessary  to  check  all  adjustments 
of  the  telescope  after  the  objective  lens  has  been 
loosened  or  removed. 

REMOVING  THE  EYE  PIECE.  If  there  is  an  eye  piece 
pinion,  first  take  out  the  two  screws  holding  it  to  the 
telescope  and  pull  the  pinion  straight  out  from  the  tube. 
Take  out  the  eye  piece  centering  screws,  A  A,  Fig.  I, 
unscrew  the  eye  end  ring,  L,  and  withdraw  the  eye 
piece  from  the  tube.  The  eye  piece  lenses  may  be 
separately  cleaned,  and,  if  put  back  as  found,  no  adjust- 
ments will  have  been  destroyed. 


66  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

CROSS  WIRE  DIAPHRAGM.  If  necessary  to  replace 
a  cross  wire  in  the  field,  the  eye  piece  must  first  be  re- 
moved, as  described  above.  With  the  telescope  in  a 
horizontal  position,  first  take  out  two  side  adjusting 
screws,  B  B,  Fig.  I,  and  by  means  of  the  remaining 
screws  turn  the  diaphragm  through  an  angle  of  90°,  so 
that  the  edge  points  toward  the  end  of  the  telescope. 
Place  a  small  stick  or  pencil  in  the  screw  hole  in  the 
side  of  the  diaphragm,  take  out  the  remaining  screws 
and  pull  out  the  diaphragm.  If  the  diaphragm  has 
adjustable  stadia  wires  the  stadia  screws  must  first 
be  loosened. 

COMPASS  NEEDLE.  The  closed  top  over  the  compass 
may  be  removed  by  unscrewing  the  bezel  ring  from  right 
to  left.  When  replacing  the  needle  on  its  center,  it 
should  be  lowered  very  gently  into  position  to  prevent 
damage  to  the  finely  polished  point. 

THE  OBJECTIVE  SLIDE.  Take  out  the  four  screws 
from  the  pinion  strap,  pull  the  pinion  straight  out  from 
the  tube,  and  the  slide  may  be  withdrawn  from  the 
telescope. 

LEVEL  VIALS.  Take  the  levels  from  the  plate,  or  the 
telescope,  and  remove  the  ends.  These  screw  on  for  the 
larger  sizes,  but  simply  push  in  the  vial  tube,  for  the 
smaller  sizes.  Soak  the  plaster  of  paris  with  water, 
scrape  or  cut  it  out,  and  push  out  the  old  vial.  If  the 
new  vial  fits  loosely,  it  should  be  fixed  in  place  with  slips 
of  paper  before  being  plastered.  Take  care  that  the 
crowning  side  of  the  vial,  which  is  graduated,  is  placed 
uppermost  and  see  that  the  sealed  tip  will  not  be  touched 


TRANSIT  INSTRUMENTS  67 

when  the  end  of  the  case  is  replaced.  If  plaster  of 
paris  is  not  available,  beeswax  or  some  other  heavy  wax 
may  be  used  temporarily  to  hold  the  vial,  but,  as  this 
softens  on  a  warm  day,  it  should  replaced  by  plaster  of 
paris  at  the  first  opportunity.  The  sealed  tip  should 
be  left  uncovered. 

To  SEPARATE  THE  PLATES.  Unscrew  the  tangent 
barrel,  taking  care  that  the  tangent  slide  and  spring  do 
not  drop  out.  Take  the  small  screws  from  the  tangent 
hanger  and  remove  the  latter  from  the  plate. 

If  the  lower  plate  or  limb  is  to  be  removed,  the  lower 
tangent  barrel  with  slide  and  spring  should  be  removed 
from  the  leveling  head  tangent. 

Remove  the  cap  (if  there  is  one)  from  the  bottom  of 
the  spindle,  take  out  the  large  screw  and  washer,  and 
the  plate  may  then  be  removed  from  the  sockets. 

The  most  extreme  care  must  be  used  in  replacing  the 
sockets  and  spindles  to  see  that  not  the  slightest  parti- 
cle of  lint  or  dust  gets  into  the  bearing.  To  lubricate 
these  surfaces,  rub  a  small  amount  of  the  very  best 
watch  oil  on  a  clean  cloth  free  from  lint,  and  rub  over 
the  surfaces  to  be  lubricated.  A  heavy  oil  will  separate 
these  bearings  so  far  that  proper  adjustment  cannot  be 
maintained. 

THE  REPAIRS.  Attention  is  again  called  to  the  fact 
that  a  damaged  instrument  should  not  be  repaired  in  the 
field.  If  any  parts  have  been  injured  the  best  way  is 
to  return  the  whole  instrument  to  us  for  proper  repairs. 
Such  repairs  can  be  made  with  less  trouble  and  less  cost 
if  no  attempt  has  been  made  to  dismount  the  instrument 
in  the  field  to  determine  the  extent  of  the  damage. 


68  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

USE  OF  THE  TRANSIT 

THE  instrument  should  be  set  up  firmly,  the  tripod 
legs  being  pressed  into  the  ground  only  so  far  as 
is  necessary  to  give  sufficient  support.  The  legs 
should  be  spread  apart  far  enough  so  that  the  transit 
cannot  be  easily  knocked  over.  The  height  of  the  instru- 
ment should  be  adjusted  for  convenient  sighting  by  the 
operator.  The  plate  should  then  be  carefully  leveled, 
as  described  hereinafter  under  level  adjustments.  For 
precise  work  the  final  leveling  of  the  plates  should  be 
made  with  the  telescope  level,  placing  it  in  turn  over 
the  two  pairs  of  opposite  leveling  screws.  In  reversing 
the  level,  one  half  of  the  correction  should  be  made  with 
the  axis  tangent  and  the  other  half  with  the  leveling 
screws,  the  same  as  in  the  adjustment  for  plate  levels. 

With  the  telescope  pointed  toward  the  sky,  or  out  of 
focus,  turn  the  eye  piece  pinion  or  the  spiral  until  the 
cross  wires  appear  distinct,  then  the  objective  should  be 
focused  until  the  object  is  seen,  clear  and  well  defined, 
and  the  wires  appear  to  be  fastened  to  its  surface. 

If  the  objective  is  properly  focused  so  that  the  plane 
of  the  image  coincides  with  the  plane  of  the  cross  wires, 
the  latter  will  not  appear  to  move  on  the  object  when  the 
eye  is  moved  up  and  down  in  front  of  the  eyepiece. 

When  the  horizontal  angles  are  to  be  measured  the 
zeros  of  the  verniers  and  limb  should  be  in  line  with  the 
upper  motion.  Clamped  in  this  position,  the  telescope 
should  be  sighted  on  a  distant  point  by  means  of  the 
lower  or  leveling  head  motion.  After  this  has  been  done 
and  'with  the  lower  motion  clamped,  loosen  the  upper 


TRANSIT  INSTRUMENTS  69 

motion  on  limb  clamp  and  the  angles  turned  may  be 
read  directly  from  the  verniers  without  making  any  sub- 
tractions. 

When  the  compass  is  to  be  used,  set  the  variation 
arc  to  the  proper  magnetic  declination  by  means  of  the 
pinion  on  the  plate.  The  value  of  magnetic  variation 
for  any  given  locality  can  be  obtained  from  the  publica- 
tions of  the  U.  S.  Geological  Survey,  Washington,  D.  C. 

If  the  needle  does  not  hang  level  when  at  rest,  re- 
move it  from  the  pivot  and  slide  the  small  brass  wire, 
which  is  on  the  South  end  (in  the  Northern  hemisphere), 
in  the  proper  direction  to  obtain  a  balance. 

STADIA  SURVEYING 

The  increasing  popularity  of  the  stadia  for  the  deter- 
mination of  distances  and  differences  in  elevation  is  due 
to  its  widening  field  of  application,  together  with  a  better 
appreciation  of  its  reliability  through  a  clearer  under- 
standing of  the  principles  involved. 

So  much  has  been  written  regarding  the  theory  of 
the  stadia  and  so  little  as  to  its  practice,  that  there  is 
need  of  a  condensed  statement  of  the  most  approved  pro- 
cedure in  stadia  work. 

The  instrumental  outfit  embraces  any  mounted  tele- 
scope fitted  with  stadia  wires  and  a  vertical  arc  or  circle, 
and  while  any  leveling  rod  may  serve  for  occasional 
stadia  work,  a  regular  stadia  rod  of  some  approved  type 
should  be  used  for  good  work,  and  must  be  used  for  sat- 
isfactory results  at  distances  exceeding  400  feet.  In  all 

cases,  simplicity  rather,  than  jnultiplicity  of  subdivision 
*  WTVERSlTr  OF  CALIFORNIA 

is  a  prime  requisite. 

-•fiFARTMENT  OF  CIVIL  ENGINES*!* 


70  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

STADIA  CONSTANT.  The  use  of  the  stadia  when 
measuring  short  distances  with  great  accuracy,  compels 
the  use  of  the  so  called  "Stadia  Constant."  The  wires 
are  generally  adjusted  to  read  one  foot  on  the  rod  at  a 
distance  of  one  hundred  feet  from  a  point  in  front  of 
the  telescope  objective  equal  to  the  focal  length  of  the 
lens  (f),  Fig.  20.  Since  measurements  are  taken  from 
the  center  of  the  instrument,  it  is  therefore  necessary  to 
add  to  the  stadia  reading,  the  distance  C,  from  the  center 
of  the  axis  to  the  shoulder  of  the  objective  setting  when 
focused  at  the  distance  to  be  measured,  plus  the  distance 
F,  from  the  objective  lens  to  the  plane  of  the  stadia 
wires,  when  the  instrument  is  focused  at  a  distant  ob- 
ject (not  less  than  1000  feet)  which  gives  the  focal 
length  of  the  lens.  The  sum  of  these  two  distances 
(F  -(-  C),  is  the  Stadia  Constant,  which  must  be  added 
to  all  stadia  measurements  regardless  of  the  distance 
measured.  This  constant  is  carefully  measured  in  the 
factory  for  each  instrument,  and  its  value  is  marked  on 
a  card  placed  in  the  instrument  box. 

For  example,  in  our  eleven  inch  telescope,  such  as 
are  used  with  the  larger  transits,  C  equals  about  5.6 
inches  and  F,  about  8.2  inches;  and  C  -f-  F  is  equal  to 
about  1.15  feet.  For  the  Mountain  Transit  telescopes, 
C  equals  4  inches  and  F,  5.4  inches,  and  C  -f-  F  equals 
about  0.783  foot. 

The  reason  for  the  use  of  this  constant  will  be  seen 
by  reference  to  Figure  20. 


TRANSIT  INSTRUMENTS  71 


With  the  telescope  focused  upon  the  rod: 
Let  i  =  interval  between  the  stadia  wires 

c  =  distance  from  center  of  transit  to  objective 

lens 

f  =  focal  length  of  objective  lens 
s  —  reading  on  the  rod,  or  space  intercepted  on 

rod  by  stadia  wires 

Outer  focus  =  a  point  in  front  of  the  lens  and  F  dis- 
tance from  it 

d  •==.  distance  from  the  outer  focus  to  the  rod 
From  the  definition  of  focal  length,  those   rays  of 
light  passing  through  the  outer  focus  are  refracted  by 
the  lens  to  parallel  paths.     Those  which  pass  through 
this  point  and  intercept  the  stadia  wires  are  i  distance 
apart  at  the  lens. 
Then  from  similar  triangles 

(1)  d/s  =  f/i,  or  d  =  f/is 

since  f/i  is  a  constant  for  any  given  instrument,  we  may 
represent  it  by  K 

(2)  and  d  =  Ks 


72:         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Since  the  measurements  are  made  from  the  center  of 
the  instrument,  we  must  add  F  +  C,  and  the  total  dis- 
tance is 

D  =  Ks  +  (F  +  C) 

(F  -]-•  C)  is  called  the  Stadia  Constant  and  K  is  made 
100  feet. 

Therefore,  if  f  -)-  c  =  1.2  feet,  a  subsequent  reading 
of  540  feet  would  indicate  a  distance  of  541.2  feet  from 
plumb  line  to  rod. 

The  undue  consideration  of  this  very  small  f  -(-  c 
constant  has  too  often  caused  the  relative  neglect  of  a 
far  more  important  one,  and  we  wish  here  to  emphasize 
the  latter. 

It  is  either  the  necessity  for  extreme  accuracy  in  ad- 
justing the  stadia  wires  to  give  the  desired  proportion 
of  1  to  100,  or,  in  the  case  of  measurements  calling  for 
greatest  precision,  the  necessity  for  determining  the 
stadia  interval  or  factor,  i.  e.,  K. 

K  =  f/i  =  d/s  =  100  ± 

This  factor  should  be  a  mean  result  of  rod  readings 
at  steel-taped  distances  of  say  400  and  700  feet  from 
a  point  f  -f-  c  in  front  of  the  center  of  the  instrument. 
E.  g.,  observed  readings  of  395.2  and  693.0  feet  would 
give  (dividing  by  400  and  700)  proportions  of  98.8  and 
99.0  to  1,  respectively,  and  a  corresponding  mean  inter- 
val factor  of  101.11  (100  divided  by  the  mean  propor- 
tion 98.9),  which,  multiplied  by  subsequent  field  read- 
ings, would  bring  the  observed  distances  up  to  the 
correct  ones.  Thus,  if  f  +  c  =  1.2  feet,  an  observed 
distance  of  230  feet  could  be  treated  as  follows:  (230  X 


TRANSIT  INSTRUMENTS  73 

1.0111)  +  1.2  =  233.75  feet  true  distance  from  center 
of  instrument  to  rod. 

In  practice,  however,  a  small  reduction  table  can  be 
quickly  prepared  to  give  these  corrected  distances  for 
every  10  feet  up  to  100,  then  each  100  feet  up  to  1,000, 
etc.  This  table  may  include  or  exclude  the  f  -|~  c 
constant. 

Stadia  wires  are  sometimes  set  so  that  the  reading 
indicates  the  exact  figure  including  the  stadia  constant 
for  some  one  distance,  and  the  slight  error  for  other  dis- 
tances is  disregarded. 

STADIA  WORK  WITH  INCLINED  SIGHTS.  If  the  tele- 
scopic line  of  sight  is  inclined  to  the  horizontal,  the 
distance  as  read  from  the  rod  must  be  corrected  accord- 
ing to  the  vertical  angle  indicated  by  that  pointing.  The 
same  data,  vertical  angle  and  observed  distance  at  that 
pointing  are  used  to  compute  difference  in  elevation 
between  instrument  and  rod.  The  lod  should  be  held 
vertical,  which  makes  the  operations  simpler  and  in 
general  more  accurate. 

To  facilitate  both  these  operations  various  stadia 
tables,  diagrams  and  slide  rules  have  been  devised.  They 
are  all  based  upon  the  well  known  stadia  formulae, 
which,  for  practical  purposes,  may  be  expressed  as: 

d  =  s  cos2v  +  (f  +  c)  cos  v  (1) 

h  =  s  %  sin  2  v  -f-  (f  _|_  c)  sin  v  (2) 

where 

s  •=  observed  stadia  distance 

v  =  measured  vertical  angle 

d  =  required  distance  from  center  of  instrument  to 
rod 

h  =  required  difference  of  elevation  between  instru- 
ment and  point  sighted  on  rod. 


74  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Stadia  diagrams  or  charts  give  the  difference  in  ele- 
vation and  also  the  reduced  horizontal  distance,  graphic- 
ally, at  a  point  in  the  chart  which  is  found  at  the 
intersection  of  two  lines,  one  representing  the  measured 
angle  and  the  other  the  observed  distance. 

Stadia  slide  rules  involve  setting  the  slide  to  corres- 
pond to  the  angle  and  then  reading  off,  opposite  the 
denoted  distance,  the  desired  results.  We  furnish  with 
each  instrument  having  stadia  wires,  but  no  Beaman 
Stadia  Arc,  a  celluloid  circular  slide  rule  known  as  the 
Cox  Stadia  Computer. 

THE  BEAMAN  STADIA  ARC  affords  a  rapid  and  exact 
mechanical  solution  of  these  functions  without  the 
necessity  of  the  measurement  of  the  usual  vertical  angle 
and  without  recourse  to  either  tables,  charts  or  slide 
rules,  and  with  but  trifling  computation.  This  practical 
and  inexpensive  patented  attachment  for  transits  and 
alidades  is  controlled  by  us  and  is  described  on  pages 
90  to  96. 

SUGGESTIONS  FOR  STADIA  WORK.  The  accuracy  of 
all  stadia  work  is  directly  proportional  to  the  ease,  care 
and  accuracy  with  which  the  observed  stadia  distance 
has  been  read.  If  either  focus  is  poor,  if  the  rod  is 
indistinct  by  reason  of  too  great  distance  or  other  cause, 
or  if  the  rod  is  not  held  plumb,  the  observed  distance  is 
uncertain,  and,  therefore,  good  results  cannot  be  ex- 
pected. 

The  greater  the  vertical  angle,  the  greater  the  error 
due  to  the  rod  not  being  held  plumb. 


TRANSIT  INSTRUMENTS  75 

Secure  such  a  focus  on  wires  as  will  give  no  apparent 
displacement  of  object  when  stadia  wires  are  in  sharp 
focus  for  the  observer  and  when  objective  is  focused  on 
object  and  eye  is  moved  up  and  down  in  front  of  eye- 
piece; i.  e.,  see  that  there  is  no  parallax. 

The  instrumental  adjustments  to  be  made  are  for 
collimation  and  level  tube. 

When  the  air  is  unsteady  or  "boiling,"  remember  that 
the  greatest  refraction  in  the  line  of  sight  occurs  in  the 
lower  air  stratum.  Therefore,  at  these  times  avoid  so 
far  as  possible  reading  a  distance  in  which  the  lower 
wire  is  nearer  the  ground  than  two  or  three  feet. 

For  refined  work,  determine  the  stadia  factor,  K, 
under  such  conditions  as  will  approximate  those  to  be 
expected  in  field  practice.  The  mid- forenoon  or  after- 
noon is  preferable  to  midday. 

For  elevation  work  with  inclined  sights,  note  the 
necessity  for  extreme  accuracy  in  the  observed  distance 
when  the  vertical  angle  is  large,  and  the  necessity  for  a 
carefully  determined  angular  value  when  the  distance 
is  great. 

THE  GRADIENTER  ATTACHMENT  No.  150,  which  may 
be  used  to  advantage  in  all  stadia  work  is  fully  described 
on  pages  96  to  100. 


76  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

TO  ADJUST  THE  TRANSIT 

EACH  Gurley  instrument  leaves  the  factory  in  com- 
plete adjustment,  but  some  adjustments  are  liable 
to  derangement  by  accident  or  careless  use.       We 
describe  particularly  those  which  are  most  likely  to  need 
attention. 

The  principal  adjustments  of  the  transit  are  the, 

Plate  Levels 

Line  of  Collimation 

Standards 

Objective  Slide 

Vertical  Circle  Vernier 

Level  on  Telescope 

To  ADJUST  THE  PLATE  LEVELS.  Set  the  instrument 
upon  its  tripod  as  nearly  level  as  may  be,  and  having 
undamped  the  plates,  bring  the  two  levels  above,  and  on 
a  line  with,  the  two  opposite  leveling  screws,  and,  turn- 
ing both  in  or  out,  as  may  be  needed,  bring  the  bubble 
of  the  level  directly  over  the  screws  exactly  to  the 
middle  of  the  opening.  Without  moving  the  fnstrument, 
proceed  in  the  same  manner  to  bring  the  other  bubble 
to  the  middle.  The  level  first  corrected  may  now  be 
thrown  a  little  out;  if  so,  bring  it  in  again,  and  when 
both  are  in  place,  turn  the  instrument  half  way  around. 
If  the  bubbles  are  both  in  the  middle  they  need  no  cor- 
rection ;  but  if  not,  turn  the  nuts  at  the  end  of  the  levels 
with  the  adjusting  pin,  until  the  bubbles  are  moved  over 
half  the  error.  Bring  the  bubbles  again  into  the  middle 
by  the  leveling  screws,  and  repeat  the  operation  until 
the  bubbles  will  remain  in  the  middle  during  a  complete 


TRANSIT  INSTRUMENTS  77 

revolution  of  the  instrument.  The  leveling  screws 
should  be  kept  free  at  first,  gradually  tightening  them 
as  final  adjustment  is  approached. 

To  ADJUST  THE  LINE  OF  COLLIMATION.  This  adjust- 
ment is  to  bring  the  cross  wires  into  such  a  position  that 
the  instrument,  when  placed  at  the  middle  of  a  straight 
line,  will,  by  the  transit  of  the  telescope,  cut  the  extrem- 
ities of  the  line.  Having  leveled  the  instrument,  deter- 
mine if  the  vertical  wire  is  plumb,  by  focusing  on  a 
defined  point  and  observing  if  the  wire  remains  on  that 
point  when  the  telescope  is  elevated  or  depressed.  If 
not,  loosen  the  cross  wire  screws,  BB,  see  Fig.  1,  and 
by  their  heads  turn  the  ring  until  correct.  The  open- 
ings in  the  telescope  tube  are  slightly  larger  than  the 
screws,  so  that  when  the  latter  are  loosened  the  ring 
can  be  rotated  a  short  distance  in  either  direction. 

Direct  the  intersection  of  the  cross  wires  on  an  ob- 
ject two  or  three  hundred  feet  distant.  Set  the  clamps, 
and  transit  to  an  object  about  the  same  distance  in  the 
opposite  direction.  Unclamp,  turn  the  plates  half  way 
around,  and  direct  again  to  the  first  object;  then  transit 
to  the  second  object.  If  it  strikes  the  same  place,  the 
adjustment  is  correct.  If  not,  the  space  which  inter- 
venes between  the  points  bisected  in  the  two  observations 
will  be  double  the  deviation  from  a  true  straight  line, 
since  the  error  is  the  result  of  two  observations. 

In  the  diagram,  Fig.  21,  let  A  represent  the  center 
of  the  instrument,  and  B  C  the  imaginary  straight 
line,  upon  the  extremities  of  which  the  line  of  collimation 
is  to  be  adjusted.  B  represents  the  object  first  selected, 


78  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

and  D  the  point  which  the  wires  bisected  when  the  tele- 
scope was  reversed. 

D 


FIG.  21 

When  the  instrument  is  turned  half  around,  and  the 
telescope  again  directed  to  B,  and  once  more  reversed, 
the  wires  will  bisect  an  object,  E,  situated  as  far  to  one 
side  of  the  true  line  as  the  point,  D,  is  on  the  other  side. 
The  space,  D  E,  is  therefore  the  sum  of  two  deviations 
of  the  wires  from  a  true  straight  line,  and  the  error  is 
made  apparent. 

In  order  to  correct  this,  use  the  two  capstan  head 
screws  BB,  Fig.  1,  on  the  sides  of  the  telescope,  these 
being  the  ones  which  affect  the  position  of  the  vertical 
wire.  It  must  be  kept  in  mind  that  the  eyepiece  appar- 
ently inverts  the  position  of  the  wires,  and  therefore, 
in  loosening  one  of  the  screws  and  tightening  the  other 
on  the  opposite  side,  the  operator  must  proceed  as  if  to 
increase  the  error  observed. 

The  wires  being  adjusted,  their  intersection  may  now 
be  brought  into  the  center  of  the  field  of  view  by  moving 
the  screws,  A  A,  which  are  slackened  and  tightened  in 
pairs,  the  movement  being  now  direct,  until  the  wires  are 
seen  in  their  proper  position. 

The  position  of  the  line  of  collimation  depends  upon 
the  relative  position  of  the  objective  and  the  cross  wires, 


TRANSIT  INSTRUMENTS  79 

so  that  the  eyepiece  may,  as  in  the  case  just  described, 
be  moved  in  any  direction,  or  even  removed  and  a  new 
one  substituted,  without  at  all  deranging  the  adjustment 
of  the  wires. 

To  ADJUST  THE  STANDARDS.  In  order  that  the  point 
of  intersection  of  the  wires  may  trace  a  vertical  line  as 
the  telescope  is  elevated  or  depressed,  it  is  necessary 
that  the  standards  of  the  telescope  should  be  of  precisely 
the  same  height.  That  is  the  center  line  of  the  horizon- 
tal axis  must  lie  in  a  plane  perpendicular  to  the  center 
line  of  the  spindle.  To  ascertain  this,  and  make  the 
correction,  if  needed,  proceed  as  follows: 

Having  the  line  of  collimation  properly  adjusted,  set 
up  the  instrument  in  a  position  where  points  of  observa- 
tion can  be  selected,  giving  a  long  range  in  a  vertical 
direction,  such  as  the  apex  and  base  of  a  lofty  spire. 

Level  the  instrument,  direct  the  telescope  to  the  top 
of  the  object,  and  claim)  to  the  spindle;  then  bring  the 
telescope  down  until  the  wires  bisect  some  well  defined 
point  at  the  base.  Turn  the  instrument  half  around, 
reverse  the  telescope  and  direct  to  the  lower  point,  clamp 
to  the  spindle,  and  raise  the  telescope  to  the  highest 
point.  If  the  wires  bisect  it,  the  vertical  adjustment  is 
effected;  if  they  are  thrown  to  either  side,  this  proves 
that  the  standard  opposite  to  that  side  is  the  highest,  the 
apparent  error  being  double  that  actually  due  to  this 
cause.  To  correct  it,  we  make  one  of  the  bearings  of 
the  axis  movable,  so  that  by  turning  a  screw  underneath 
this  sliding  piece,  as  well  as  the  screws  which  fasten  the 
cap  of  the  standard,  the  adjustment  is  made  with  pre- 


80  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

cision.        If  the  standards  adjustment  is  altered,  it  is 
necessary  to  again  adjust  the  line  of  collimation. 

Besides  the  three  adjustments  described,  which  are 
all  that  the  surveyor  will  ordinarily  be  required  to  make, 
there  are  other  adjustments  of  the  transit  which  may 
sometimes  be  necessary. 

To  ADJUST  THE  OBJECTIVE  SLIDE.  In  case  of  acci- 
dent or  injury,  it  may  be  necessary  to  adjust  the  objec- 
tive slide,  and  this  should  be  done  as  follows.  First 
make  sure  that  the  vertical  wire  is  as  nearly  plumb  as 
it  is  possible  to  make  it.  Having  set  up  and  leveled  the 
instrument,  the  line  of  collimation  being  adjusted  for 
objects  from  three  hundred  to  five  hundred  feet  distant, 
clamp  the  plates,  and  fix  the  vertical  cross  wire  upon  an 
object  as  distant  as  may  be  distinctly  seen.  Without 
disturbing  the  instrument,  move  out  the  objective  so  as 
to  bring  the  vertical  wire  upon  an  object  as  near  as  the 
range  of  the  telescope  will  allow.  Having  this  object 
clearly  in  mind,  loosen  the  upper  clamp,  turn  the  instru- 
ment half  way  around,  reverse  the  telescope,  clamp  the 
instrument,  and  with  the  tangent  screw  bring  the  vertical 
wire  again  upon  the  near  object;  then  draw  in  the  objec- 
tive until  the  distant  object  first  sighted  upon  is  brought 
into  distinct  vision.  If  the  vertical  wire  strikes  the 
same  line  as  at  first,  the  slide  is  correct  for  both  near 
and  remote  objects,  and,  being  itself  straight,  is  correct 
for  all  distances. 

But  if  there  is  an  error,  proceed  as  follows:  With  a 
screw  driver  turn  the  two  screws,  CC,  Fig.  1,  on  the 
opposite  sides  of  the  telescope,  loosening  one  and  tight- 


TRANSIT  INSTRUMENTS  81 

ening  the  other,  so  as  to  apparently  increase  the  error, 
making,  by  estimation,  one  half  the  correction  required. 
Then  go  over  the  usual  adjustment  of  the  line  of  collim- 
ation,  and,  having  completed  it,  repeat  the  operation 
above  described,  first  sighting  upon  the  distant  object, 
then  upon  a  near  one  in  line,  then  reversing,  making  cor- 
rections, etc.,  until  the  adjustment  is  complete. 

This  adjustment  is  a  distinctive  feature  of  Gurley 
transits  and  furnishes  the  only  way  in  which  the  line  of 
collimation  can  be  correct  for  all  distances. 

To  ADJUST  THE  VERTICAL  CIRCLE  VERNIER.  Having 
the  instrument  firmly  set  up  and  carefully  leveled  by 
means  of  the  telescope  level,  bring  into  line  the  zeros  of 
the  circle  and  vernier,  and  with  the  telescope  find  some 
well  defined  point,  from  one  hundred  to  five  hundred 
feet  distant,  which  is  cut  by  the  horizontal  wire.  Turn 
the  instrument  half  way  around,  transit  the  telescope, 
and  fixing  the  wire  upon  the  same  point  as  before,  ob- 
serve if  the  zeros  are  again  in  line.  If  not,  loosen  the 
capstan  head  screws  which  fasten  the  vernier,  and  move 
the  zero  of  the  vernier  over  half  the  error;  bring  the 
zeros  again  into  coincidence,  and  proceed  exactly  as  be- 
fore, until  the  error  is  entirely  corrected. 

In  most  cases  the  error  is  slight  and  may  be  best 
removed  by  putting  the  zeros  in  line  and  making  the 
adjustment  by  the  horizontal  wire,  moving  it  by  the 
vertical  capstan  head  screws  until  the  vertical  circle  will 
reverse  on  the  same  point. 

To  ADJUST  THE  LEVEL  ON  TELESCOPE.  When  the 
vernier  of  the  vertical  circle  is  adjusted  and  is  at  zero, 


82  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

the  line  of  collimation  is  level  and  the  bubble  may  be 
brought  into  the  middle  of  its  run  by  the  capstan  head 
nuts. 

Another  method  is  as  follows:  First  level  the  instru- 
ment carefully,  using  the  telescope  level  and  with  the 
clamp  and  tangent  movement  to  the  axis  make  the  tele- 
scope as  nearly  horizontal  as  may  be,  by  the  eye.  Then, 
having  previously  adjusted  the  line  of  collimation,  drive 
a  stake  at  a  convenient  distance,  say  from  one  hundred 
to  three  hundred  feet,  and  note  the  height  cut  by  the 
horizontal  wire  upon  a  staff  set  at  the  top  of  the  stake. 

Fix  another  stake  in  the  opposite  direction  and  at 
the  same  distance  from  the  instrument,  and  without  dis- 
turbing the  telescope  turn  the  instrument  upon  its 
spindle,  set  the  staff  upon  the  stake,  and  drive  the  stake 
into  the  ground  until  the  same  height  is  indicated  as  in 
the  first  observation.  The  tops  of  the  two  stakes  will 
then  be  in  the  same  horizontal  line,  however  much  the 
telescope  may  be  out  of  level. 

Remove  the  instrument  from  fifty  to  one  hundred 
feet  to  one  side  of  either  of  the  stakes  and  in  line  with 
both.  Again  level  the  instrument,  clamp  the  telescope 
as  nearly  horizontal  as  possible,  and  note  the  heights 
indicated  upon  the  staff  placed  first  upon  the  nearest  and 
then  upon  the  'most  distant  stake.  If  both  agree,  the 
telescope  is  level.  If  they  do  not  agree,  with  the  tan- 
gent screw  move  the  wire  over  nearly  the  whole  error, 
as  shown  at  the  distant  stake,  and  repeat  the  operation 
just  described.  Proceed  thus  until  the  horizontal  wire 
will  indicate  the  same  height  at  both  stakes,  when  the 


TRANSIT  INSTRUMENTS  83 

telescope  will  be  truly  horizontal.  Taking  care  not  to 
disturb  the  position  of  the  telescope,  bring  the  bubble 
into  the  middle  by  the  leveling  nuts  at  the  end  of  the 
tube,  when  the  adjustment  will  be  complete. 

REPAIRS.  When  an  instrument  becomes  worn  from 
service  or  is  injured  by  a  fall  or  accident  of  any  kind, 
it  is,  of  course,  necessary  to  have  it  repaired  and  refitted 
before  anyone  can  adjust  it. 

An  instrument  in  need  of  repairs  should  be  sent 
directly  to  us,  as  our  facilities  enable  us  to  do  the  work 
economically  and  promptly.  Always  place  the  instru- 
ment in  its  own  case,  wrap  with  paper,  then  enclose  in 
an  outside  packing  case,  at  least  an  inch  larger  in  all  its 
dimensions  and  fill  the  space  between  the  two  with  paper 
wadding,  hay  or  shavings. 

ATTACHMENTS  FOR  TRANSITS 

IN  the  use  of  the  transit  it  is  generally  found  advisable 
to  add  one  or  more  attachments  to  the  telescope.    All 
Gurley  transits  and  their  attachments  are  made  to 
standard    sizes,   so   that    one    or   more    of   these   useful 
accessories  can  be  fitted  to  the  instrument  at  any  time. 

When  any  of  these  attachments  are  desired,  either 
for  our  instruments  or  those  of  other  makers,  the  instru- 
ment must  be  sent  to  us.  Occasionally  they  can  be 
added  by  a  skillful  mechanic  nearer  the  customer,  but 
this  is  generally  more  expensive  and  less  satisfactory. 


84  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The    principal    attachments     for    the     transit     are 
described  on  the  following  pages,  and  are: 

VERTICAL  CIRCLE  (see  pages  85  to  87). 
GUARD  FOR  VERTICAL  CIRCLE   (see  page  85). 
VERTICAL  ARC  (see  page  88). 
LEVEL  ON  TELESCOPE   (see  page  89). 
BEAMAN  STADIA  ARC   (see  pages  90  to  96). 
GRADIENTER,  COMBINED  WITH  CLAMP  AND  TANGENT 

(see  pages  96  to  100). 
DETACHABLE   TELESCOPES   FOR  VERTICAL     SIGHTING 

(see  pages  101  and  102). 
REFLECTOR    FOR    ILLUMINATING    THE    CROSS    WIRES 

(see  page  103). 
DIAGONAL     PRISM    FOR    EYEPIECE     OF     TELESCOPE 

(see  page  103). 

PLUMMET  LAMP  (see  page  104). 
ATTACHED  MAGNIFIERS  TO  HORIZONTAL  OR  VERTICAL 

LIMB  (see  page  106). 
BURT  SOLAR  ATTACHMENT  TO  TELESCOPE  (see  pages 

114  to  136). 

SOLAR  SCREEN   (see  page  106). 
TELESCOPIC    SOLAR    ATTACHMENT    (see    pages    136 

to  144). 


TRANSIT  INSTRUMENTS 


85 


FIG.  22 

No.   136  VERTICAL   CIRCLE,  WITH 
No.  141  ALUMINUM  GUARD 


THE  VERTICAL  CIRCLE.  Vertical  Circle,  No.  136, 
is  graduated  on  sterling  silver  and  figured  in  quadrants 
0  to  90  each  way.  We  make  three  sizes,  four  inches, 
four  ai-d  one-half  inches  and  five  inches  in  diameter,  all 
reading  by  one  fixed  vernier  to  single  minutes. 

There  is  an  adjustment  on  the  hub  by  which  the  grad- 
uations are  as  accurately  and  permanently  centered  as 
those  of  the  horizontal  limb. 


86 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


FIG.  23 
No.  138  VERTICAL  CIRCLE,  WITH  TWO  OPPOSITE  DOUBLE 

VERNIERS,   AND   GUARD 


The  four  inch  and  five  inch  vertical  circle  may  be 
arranged  as  shown  in  No.  138,  to  be  read  by  two  opposite 
double  verniers  to  one  minute.  The  verniers  are  sup- 
ported on  a  ribbed  frame  or  guard  in  such  a  manner 
that  the  circle  is  concentric  with  the  frame,  and  the 
verniers  read  accurately  in  any  position  of  the  circle. 

The  frame  is  arranged  with  an  adjusting  screw,  to 
bring  the  verniers  into  exact  adjustment  with  the  level 
on  the  telescope. 


TRANSIT  INSTRUMENTS 


87 


Fm.  24 

No.  139  VERTICAL  CIRCLE,  4.5  INCHES  DIAMETER,  WITH 

GRADUATIONS  ON  EDGE  OR  RIM,  PROTECTED  BY  A  METAL 

GUARD.     CIRCLE  GRADUATED  TO  HALF  DEGREES, 

WITH  VERNIER  READING  TO    1    MINUTE. 


If  desired  the  vertical  circle  can  be  graduated  on  the 
edge  or  rim,  so  that  the  vernier  is  visible  in  front  of 
the  observer  without  a  change  of  position.  As  on 
No.  138  the  vernier  is  attached  to  the  guard,  instead  of 
to  the  standard.  The  adjustment  is  made  in  the  same 
manner  as  it  is  on  the  regular  pattern,  No.  136. 

GUARD  FOR  VERTICAL  CIRCLE.  All  transits  having 
a  vertical  circle  should  be  equipped  with  a  guard,  to 
protect  the  graduated  edge  of  the  circle.  We  make  an 


88  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

improved  guard,  shown  in  No.141,  Fig.  22,  of  aluminum, 
morocco  finished,  mounted  on  the  standard  concentric 
with  the  circle  and  attached  so  that  it  can  be  removed  or 
put  in  place  without  affecting  the  adjustment  of  the 
circle. 


FIG.  25 
Nos.  139-A,  139-B  AND  140  VERTICAL  ARCS 

VERTICAL  ARC.  The  Vertical  Arc  is  made  in  three 
sizes,  of  two,  two  and  one-half,  and  three  inches  radius. 
It  is  graduated  on  sterling  silver  and  reads  by  vernier 
to  one  minute.  The  vernier  is  swung  from  the  axis  and 
is  movable  by  a  tangent  screw. 

The  arc  is  less  liable  to  damage  than  the  full  circle. 
It  was  first  introduced  to  allow  the  Burt  Solar  Attach- 
ment to  reverse.  On  Gurley  Transits  the  arc  is  movable 
around  its  bearing  on  the  axis,  and  it  may  be  clamped 
at  approximate  zero  when  the  telescope  is  level  and  the 
vernier  brought  to  exact  coincidence  of  zero,  by  a  tan- 


TRANSIT  INSTRUMENTS  89 

i 

gent  screw  that  moves  the  vernier  only.  This  Gurley 
feature  prevents  any  damage  to  the  arc  when  the  tele- 
scope is  used  in  the  reversed  position.  Any  vertical 
angle  can  then  be  read  directly  on  the  arc.  This  arc 
can  be  readily  attached  to  any  transit  of  our  manufac- 
ture. 


FIG.  26 
No.  145  LEVEL  ON  TELESCOPE 

LEVEL  ON  TELESCOPE.  The  Level  on  Telescope, 
No.  145,  consists  of  a  brass  tube  about  six  and  one-half 
inches  long,  each  end  of  which  is  held  between  two  cap- 
stan nuts  connected  with  a  screw  or  stem  attached  to  the 
under  side  of  the  telescope  tube. 

The  vial  enclosed  in  the  tube  is  a  little  over  five 
inches  long  and  half  an  inch  in  diameter,  and  is  ground 
on  its  inner  surface  so  as  to  insure  an  even  movement  of 
the  bubble,  the  length  of  which  is  measured  by  a  scale 
etched  on  the  glass.  The  scale  is  graduated  to  two 
millimeters. 


90  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

When  required  we  supply  a  tube  with  a  double  open- 
ing, and  a  Reversion  Level  Vial,  No.  146,  that  can  be 
used  either  side  up  with  equal  facility. 

Special  attention  is  called  to  the  Gurley  feature  of 
having  the  level  vial  as  nearly  as  practicable  the  full 
length  of  the  telescope.  This  gives  increased  accuracy 
in  leveling  operations. 

To  adjust  the  level  on  telescope,  see  method  described 
on  page  81. 

SIGHTS  ON  TELESCOPE  AND  ON  STANDARDS.  For  con- 
venience in  observation,  we  occasionally  place  a  pair  of 
small  sights,  No.  157,  on  the  telescopes  of  our  transits. 
These  sights  have  folding  joints,  that  they  may  lie  close 
to  the  telescope  when  not  in  use.  Sights,  No.  158,  may 
also  be  placed  on  the  standards  at  an  angle  of  ninety 
degrees  with  the  telescope,  for  use  in  offsetting. 

BEAMAN  STADIA  ARC 

THE   Beaman  Stadia  Arc  is  manufactured  only  by 
W.  &  L.  E.  Gurley,  was  devised  and  patented  by 
W.  M.  Beaman,  a  topographer  in  the  United  States 
Geological  Survey,  and  is  now  extensively  used  by  that 
bureau    in    its    topographical    surveys.        In    1906    we 
introduced  it  on  our  transits  and  alidades,  and  because 
this  arc  furnishes  engineers    with    a    rapid    and    exact 
mechanical  solution  of  the  stadia  problem,  the  use  of 
the    stadia    in    surveying   has    been   popularized   to    an 
appreciable  extent. 

By  the  use  of  this  arc  precise  differences  in  elevation, 
and  reduced  horizontal  distances  can  be  determined  with 


TRANSIT  INSTRUMENTS  91 

great  rapidity,  and  without  the  intricate  calculation  here- 
tofore necessary. 

The  arc  is  attached  to  the  vertical  limb  of  the  transit 
Fig.  9,  or  alidade  Figs.  97  and  98,  and  carries  two  scales 
having  coincident  zero  points,  marked  0  and  50  respec- 
tively, either  scale  being  read  by  an  index  common  to 
both.  The  scale  graduations  are  so  spaced  and  figured 
as  to  give  simple  multiples  of  the  rod  interval. 

The  Beaman  Stadia  Arc  can  also  be  used  for  metric 
measurements,  as  the  graduations  are  based  on  a  ratio 
of  1  to  100,  which  is  1  foot  to  100  feet,  or  1  meter  to 
100  meters.  The  stadia  constant  should  be  transposed 
to  meters,  however,  when  this  unit  is  used. 

ADVANTAGES  OF  THE  BEAMAN  STADIA  ARC 

1.  The  use  of  stadia  tables,  slide  rules,  or  diagrams  is 

entirely  obviated. 

2.  There  is  no  vernier  or  similar  contrivance  to  be  read. 

3.  Final  results  are  obtained  in  less  than  one-third  the 

time  required  by  ordinary  methods. 

4.  The  accuracy  of  results  is  identical  with  formulae 

or  table  computations,  regardless  of  the  angle  or 
distance. 

5.  The  simplicity  of  the  process  practically  eliminates 

the  chances  of  error  incidental  to  the  use  of  other 
methods. 


92 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


H  V 


0-5Q- 


66: 


FIG.  27 
GRADUATIONS 
OF  BEAMAN 
STADIA  ARC 


The  Beaman  Stadia  Arc  can  be 
supplied  with  any  new  transit  or  tele- 
scopic alidade  of  our  manufacture  having 
a  vertical  limb  of  either  a  one  vernier 
vertical  circle,  a  two  vernier  circle,  or  a 
vertical  arc.  This  attachment  can  also 
be  fitted  to  any  old  Gurley  transit  or 
telescopic  alidade,  but  the  additional 
cost  of  alterations  and  readjusting  can 
only  be  determined  upon  examination  of 
the  instrument,  which  must  be  in  our 
hands  for  this  purpose. 

For  view  of  the  graduations  of  the 
Beaman  Stadia  Arc  as  applied  to  tele- 
scopic alidades,  see  Fig.  27. 


To  obtain  difference  in  elevation  between  instrument 
and  rod  the  scale  marked  Vert,  is  used.  This  scale 
indicates  multiples  of  the  rod  interval,  for  determining 
differences  in  elevation  between  instrument  and  rod. 
The  zero  point  of  this  scale  is  marked  50,  so  a  scale 
reading  less  than  50  indicates  that  the  telescope  is  de- 
pressed, while  a  reading  greater  than  50  shows  that 
the  telescope  is  elevated. 


TRANSIT  INSTRUMENTS  93 

A  unique  feature  of  the  use  of  the  multiple  scale  is 
that  only  such  inclinations  of  the  telescope  need  be  used 
as  will  give  a  whole  number  vertical  scale  reading,  while 
the  fractional  part  of  the  elevation  is  shown  by  the  rod 
reading. 

To  obtain  the  desiied  multiple,  therefore,  sight  any- 
where on  the  rod,  it  does  not  matter  where,  so  that  a 
whole  number  reading  is  obtained  on  the  multiple  scale. 

Subtract  50  from  this  scale  reading  and  use  the  alge- 
braic remainder;  e.  g.,  if  the  Vert,  scale  reads  56,  the 
multiple  is  56 — 50=  -|- 6.  If  this  scale  reads  47,  the 
multiple  is  47 — 50= — 3. 

Example:  Suppose  the  observed  subtended  stadia 
reading  on  the  rod  to  be  6.40  (640  ft.),  and  to  obtain 
a  whole  number  for  the  scale  reading,  the  telescope  is 
inclined  so  that  the  multiple  scale  reads  33,  at  which 
setting  the  middle  wire  reads  7.30  on  the  rod. 

Then  the  desired  multiple  equals 
33  — 50  =  — 17 
and  —  17  X  6.40  =  —  108.8 

Difference  in  elevation  between  instrument  and  base 
of  rod  is  then, 

—  7.30  —  108.8  =  —  116.1   ft. 

The  negative  sign  indicates  that  the  point  where  the 
rod  was  held  is  lower  than  the  instrument. 

For  accurate  work  at  the  higher  angles  it  is  also 
necessary  to  add  to  the  difference  in  elevation  the  cor- 
rection for  the  stadia  constant,  f  -[-  c.  This  correction 
is  (f  -f-  c)  sin  vertical  angle. 


94 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


THE  TRUE  HORIZONTAL  DISTANCE  is  found  by  means 
of  the  scale  marked  "Hor.",  which  gives  at  the  same 
pointing  a  direct  reading  of  the  percentage  of  correction 
(always  subtractive)  necessary  to  reduce  the  observed 
stadia  reading  (in  feet  subtended)  to  the  true  horizontal 
distance. 

Example:  At  the  above  setting  the  reduction  scale 
would  read  3,  or  3%. 

3%  of  640  ft.  =  19.2  ft. 

640 — 19.2  =  620.8  ft.,  the  true  horizontal  distance. 

If  the  accuracy  desired  requires  the  use  of  the  stadia 
constant,  (/  -f-  c)  cos  vert,  angle  should  be  added  to  the 
horizontal  distance  as  determined  above. 

A  FORM  OF  NOTES  FOR  USE  WITH  BEAMAN  STADIA  ARC 

(Reprinted  by  permission  of  United  States 

Geological  Survey} 

To  facilitate  the  slight  computation  necessary  to 
determine  differences  in  elevation,  a  special  form  of 
notes  has  been  devised  for  use  with  this  attachment. 


Stadia  Arc 

Reading 

Distance 

Product 

Rod 
Correction 

Difference 
of 
Elevation 

Elevation 

Station 

B.  S. 

F.  S. 

654.7 

B.  M. 

54 

4.2 

-  16.8 

+  8.2 

—  8.6 

646.1 

H.  I. 

48 

6.3 

—  12.6 

—  4.9 

—17.5 

628.6 

T.  P. 

44 

9.2 

+  55.2 

+  4.3 

+59.5 

688.1 

H.  I. 

57 

15.8 

+110.6 

—13.8 

+96.8 

784.9 

T.  P. 

50 

8.4 

+  6.7 

+  6.7 

791.6 

H.  I. 

50 

5.6 

—  9.8 

—  9.8 

781.8 

T.  P. 

TRANSIT  INSTRUMENTS  95 

The  Beaman  Arc  reading  is  placed  under  the  appro- 
priate heading,  B.  S.  or  F.  S.,  in  the  above  table.  All 
sights  are  to  be  regarded  as  foresights,  except  those 
taken  to  determine  the  H.  I.  Thus,  after  a  B.  S.  has 
been  taken  to  determine  the  H.  I.,  all  intermediate  rod 
stations,  whether  taken  before  the  rod  reaches  the  instru- 
ment or  after  the  rod  goes  ahead,  are  to  be  entered  as 
foresights. 

The  distance  is  recorded  as  4.2,  6.3,  etc.,  meaning 
420  feet,  630  feet,  etc. 

The  column  headed  "Product"  is  for  the  multiple 
times  the  distance;  for  example  4  X  4.2  —  16.8;  4  being 
the  multiple  for  a  stadia  arc  setting  of  54. 

The  column  headed  "Rod  Correction"  is  for  the  final 
reading  of  the  middle  wire  on  the  rod. 

The  signs  to  be  affixed  to  the  "Product"  and  to  the 
"Rod  Correction"  are  determined  according  to  whether 
the  observation  is  a  B.  S.  or  a  F.  S.,  by  following  a  rule 
of  universal  application,  namely : 


Product 

Rod  Correction 

B.  S. 
F.  S. 

Opposite  sign  to  that  indicated  by  arc  reading... 
Same  sign  as  that  indicated  by  arc  reading  

+ 

A  stadia  arc  reading  of  54  indicates  -j- ;  therefore, 
here  the  sign  of  the  "Product"  is  —  for  a  B.  S.,  and  -f- 
for  a  F.  S. 

Note  that  the  sign  of  the  "Rod  Correction"  is  the 
same  as  in  leveling. 

When  the  line  of  sight  is  level,  the  stadia  reading  is 
50,  and  hence  the  multiple  is  0,  which  gives  a  "Product" 


96 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


0.  The  only  entry  is,  therefore,  the  "Rod  Correction," 
or  the  final  rod  reading,  whose  sign  follows  the  above 
rule. 

Take  the  "Product"  and  the  "Rod  Correction"  by 
pairs,  and  add  algebraically;  e.  g.,  — 16.8  -f-  8.2= — 8.6, 
the  "Difference  of  Elevation."  This,  applied  algebrai- 
cally to  the  last  known  elevation,  gives  the  elevation 
desired. 

GRADIENTER 


FIG.  28 
No.  150,  GRADIENTER 


TRANSIT  INSTRUMENTS  97 

THE  GRADIENTER 

THIS  attachment  is  a  modification    of    the    tangent 
screw  attached  to  the  horizontal  axis  of  the  tele- 
scope, and  is  used  in  measuring  small  vertical  angles 
in  terms  of  their  tangents.       It  is  useful  in  measuring 
distances,  establishing  grades,  and  similar  work. 

It  consists  of  a  screw  accurately  cut  to  a  determined 
number  of  threads  which,  passing  through  an  eccentric 
sleeve  nut  on  one  side  of  the  arm,  presses  against  the 
small  stud,  A,  fixed  to  the  inside  of  the  right-hand  stand- 
ard. A  drum  having  a  rim  of  sterling  silver  is  adjust- 
ably centered  on  the  micrometer  screw.  This  drum  is 
graduated  into  100  equal  parts  and  a  short  arm  carries 
a  small  scale,  graduated  to  read  complete  turns  of  the 
micrometer  screw,  which  serves  as  an  index  to  the  mi- 
crometer drum.  Pressing  against  the  opposite  side  of 
the  stud  is  an  enclosed  spiral  spring  which  maintains  a 
positive  movement  of  the  Gradienter  screw. 

USE    OF   THE    GRADIENTER 

The  Gradienter  can  be  used  for  the  determination 
of  vertical  angles  less  than  6°  from  the  horizontal  and 
also  for  the  determination  of  horizontal  distances,  with- 
out reading  the  vernier  on  the  vertical  circle. 

DETERMINING  DIFFERENCES  IN  ELEVATION.  The 
initial  reading  for  each  determination  should  be  taken 
when  the  graduated  edge  of  the  drum  is  near  the  zero 
mark  on  the  index  bar. 

For  a  depression  angle,  the  center  cross-hair  of  the 
telescope  is  placed  on  the  H..  I.  point  of  the  rod  and 
the  reading  of  the  micrometer  is  noted,  using  the  nearest 


98  W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

even  division  for  general  work  and  nearest  one  half 
division  for  close  work.  (The  reading  need  not  be 
zero,  but  may  be  any  number  from  0  .to  100.)  The 
micrometer  is  then  turned  until  the  instrument  is  level, 
the  whole  turns  of  the  drum  (each  equal  to  100  divisions) 
being  counted  or  noted  on  the  scale  as  the  screw  is 
revolved.  When  the  level  bubble  is  centered,  the  read- 
ing of  the  micrometer  is  noted,  and  the  difference 
between  the  two  readings,  plus  100  for  each  whole  turn 
of  the  screw  determines  the  angle.  For  example,  if  the 
initial  reading  is  20  and  is  followed  by  two  turns  of 
the  screw  and  a  final  reading  of  32,  the  angle  is  equal 
to  212  divisions.  As  the  screw  is  so  cut  that  one  com- 
plete turn  intercepts  one  foot  on  a  rod  held  100  feet 
away,  the  difference  in  elevation  is  2.12,  times  the  dis- 
tance divided  by  100.  As  the  distances  are  measured 
from  the  center  of  the  instrument  there  is  no  stadia 
constant. 

For  an  angle  of  elevation  the  procedure  is  the  same, 
except  that  the  instrument  is  first  leveled,  the  initial 
reading  on  the  micrometer  taken,  and  the  telescope  is 
then  turned  upward  to  the  H.  I.  point  on  the  rod. 

DISTANCE  MEASUREMENTS.  Under  ordinary  condi- 
tions, for  shots  up  to  1500  feet  in  length,  the  usual 
method  of  reading  the  stadia  interval  on  the  rod  will 
probably  be  preferred  but  for  the  occasional  long  shots 
that  are  unavoidable  in  a  traverse,  and  for  work  in  hazy 
weather,  the  gradienter  determination  of  distance  is 
much  more  accurate  and  is  easier  to  read. 


TRANSIT  INSTRUMENTS  99 

To  determine  the  distance,  the  zero  of  the  microm- 
eter drum  is  set  opposite  a  division  of  the  scale.  Using 
the  center  cross-wire  set  the  target  near  the  bottom  of  a 
rod  held  on  the  point,  the  distance  to  which  is  desired. 
Read  the  target  setting.  Rotate  the  drum  one  complete 
turn  and  again  set  the  target.  Read  the  second  target 
setting.  The  number  of  hundredths  of  a  foot  difference 
between  the  two  target  settings  will  be  the  distance 
in  feet. 

As  it  is  desirable  to  read  as  great  an  intercept  on 
the  rod  as  possible,  it  is  sometimes  necessary  to  read 
more  than  one  complete  turn  of  the  micrometer  screw. 
In  general  the  distance  equals  the  rod  intercept  in  feet 
divided  by  the  number  of  turns  of  the  micrometer  drum, 
the  quotient  multiplied  by  one  hundred.  For  example : 
Drum  reading  2.85  Rod  reading  0.246 

Drum  reading         4.63  Rod  reading  13.128 

Turn  of  Drum  =  1.78  Rod  intercept         12.882 

1  o     CCO 

Distance  =  ^  -  x  100  =  723.7  feet. 

1 .  I  o 

Where  this  measurement  is  made  on  a  heavy  slope, 
the  correct  horizontal  distance  is  obtained  by  using 
stadia  i eduction  methods. 

The  original  setting  of  the  drum  should  be  such  that 
the  screw  can  be  rotated  in  a  right  hand  direction. 

ESTABLISHING  GRADES.  One  of  the  most  important 
uses  of  the  Gradienter  is  in  establishing  grades  in  sur- 
veying connected  with  railroads,  streets,  highways, 
sewers,  canals,  irrigation  ditches,  etc.  The  procedure 
is  as  follows:  First,  level  the  instrument:  Bring  the 


100        W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

telescope  level  to  its  center  by  the  clamp  and  the  grad- 
ienter  screws ;  keeping  the  telescope  level,  the  graduated 
head  may  be  turned  on  its  shaft  until  its  zero  is  brought 
to  the  edge  of  the  scale;  then  turn  off  as  many  spaces 
on  the  head  as  there  are  hundredths  of  feet  to  the  hun- 
dred in  the  grade  to  be  established. 

To  avoid  the  possibility  of  error,  observations  should 
be  taken  by  turning  the  screw  always  in  the  clock  wise 
direction  for  the  same  series  of  observations. 

The  Gradienter  drum  and  the  index  are  graduated 
on  sterling  silver ;  thus  the  graduations  are  even,'  distinct 
and  permanent.  The  entire  attachment  is  of  such  con- 
struction and  workmanship  that  it  can  be  depended 
upon  for  accurate  work. 

See  illustrations  of  Transit  No.  10- A,  Fig.  11,  and 
Transit  No.  10-A-3,  Fig.  14. 

ADJUSTMENT  OF  THE  GRADIENTER 
In  the  Gurley  Gradienter  attachment  the  value  of 
the  screw  thread  is  such  that  a  complete  revolution  of 
the  screw  will  move  the  horizontal  cross  wire  of  the 
telescope  over  a  space  of  one  foot  on  a  rod  held  at  a 
distance  of  100  feet.  If  the  screw  is  turned  through 
fifty  spaces  on  its  graduated  head,  the  wire  will  pass 
over  fifty  one-hundredths,  or  one-half  foot  on  the  rod, 
and  so  on  in  the  same  proportion.  The  same  ratio 
applies  to  metric  measurements,  1  meter  to  100  meters. 
If  this  condition  does  not  obtain,  loosen  the  hexa- 
gonal nuts  and  turn  the  eccentric  to  the  right  or  left 
thus  lengthening  or  shortening  the  arm  until  the  ratio 
is  as  required. 


TRANSIT  INSTRUMENTS 


101 


FIG.  29 

Nos.  160  AND  161  DETACHABLE  SIDE  AND  RIDING  TELE- 
SCOPES, FOR  VERTICAL  SIGHTING  IN  MlNE  SURVEYING 


1 0-2.      .W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

•DETACHABLE  TELESCOPES  FOR  VERTICAL  SIGHTING 
IN  MINE  SURVEYING 

A  convenient  arrangement  for  sighting  up  or  down  a 
vertical  shaft  is  shown  in  No.   160,    in    which    an 
extra  telescope  is  fitted  with  a  flange  and  disk  con- 
necting it  with  the  axis,    so    as    to    make    it    precisely 
parallel  with  the  main  telescope.       A  counterpoise,  as 
shown,  is  fitted  to  the  other  end  of  the  axis,  and  both 
telescope  and  counterpoise  can  be  detached  and  placed 
in  the  transit  box  when  not  in  use. 

In  No.  161,  the  extra  telescope  is  connected  with  the 
main  telescope  by  coupling  nuts,  which  fasten  it  directly 
over  the  center  of  the  instrument  and  allow  its  ready 
removal  and  replacement  without  disturbing  its  adjust- 
ments. In  both  arrangements  the  extra  telescope  is 
adjusted  to  the  main  telescope  of  the  transit  so  that  the 
lines  of  collimation  of  both  are  parallel  and  in  the  same 
plane,  horizontal  in  No.  160  and  vertical  in  No.  161; 
and  in  both,  the  extra  telescope  swings  over  the  outside 
of  the  transit  plates.  The  diagonal  prism,  No.  168,  is 
often  used  with  the  extra  telescope  for  greater  conven- 
ience in  sighting. 

REFLECTORS  FOR  ILLUMINATING  CROSS  WIRES.  Nos. 
165  and  166,  are  elliptical  pieces  of  silver  inclined  at  an 
angle  of  forty-five  degrees  with  the  ring,  which  is  fitted 
to  the  objective  end  of  the  telescope.  The  opening  of  the 
reflector  allows  the  use  of  the  telescope,  while  a  light 
held  near  the  inner  surface  illuminates  the  cross  wires. 
No.  165  is  for  transits  and  No.  166  is  for  levels. 


TRANSIT  INSTRUMENTS 


103 


FIG.  30 
NOS.  165  AND  166  CROSS  WIRE  ILLUMINATING  REFLECTORS 

THE  DIAGONAL  PRISM,  No.  168,  is  used  when  it  is 
necessary  to  observe  greater  vertical  angles  than  can  be 
taken  with  the  ordinary  telescope.  It  consists  of  a 

prism  attached  to 
the  cap  of  the 
eyepiece  by 
means  of  which 
the  image  of  the 
object  is  reflect- 
ed through  a 
right  angle  to  the 
eye.  When  the 
telescope  is  di- 
rected to  the 
sun,  a  slide 

containing  colored  glass  is  moved  over  the  opening  to 
eliminate  the  glare. 


FIG.   31 
NO.   168  DIAGONAL  PRISM 


104         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


The  circular  plate  to  which  the  prism  is  attached  is 
made  to  turn  in  the  cap,  so  that,  when  it  is  substituted 
for  the  ordinary  cap  of  the  eyepiece,  the  opening  of  the 

prism  can  be  easily  adjusted 
to  the  position  of  the  eye. 
Observations  can  be  taken 
with  the  prism  up  to  an 
angle  of  sixty  degrees  ele- 
vation. 

THE  PLUMMET  LAMP,  No. 
170,  is  a  large  plummet,  of 
which  the  upper  part  is  hol- 
low to  contain  oil.  It  has  a 
tube  with  a  wick,  and  an 
extinguisher. 

It  is  hung  in  gimbals  by 
chains  with  a  hook,  and  so 
always  assumes  a  vertical 
position,  and  when  suspend- 
ed from  the  shifting  center 
of  a  leveling  head  it  can  be 
easily  adjusted  over  a  given 
point. 

These  lamps  are  packed 
in  a  wooden  case,  furnished 
with  a  strap  to  sling  over 
the  shoulders.  The  weight  of 
each  lamp  is  about  one  and 
one-quarter  pounds,  and 
either  one,  two,  or  three  may 
be  packed  in  a  single  box. 


FIG.  32 
170  PLUMMET  LAMP 


TRANSIT  INSTRUMENTS  105 

PATENTED  LATITUDE  LEVEL,  No.  193,  is  used  for 
recovering  the  latitude  on  a  solar  transit  without  referr- 
ing to  the  vertical  arc,  and  also  for  setting  the  telescope 
at  any  desired  angle  in  running  grades  and  similar  work. 

It  consists  of  a  level  connected  by  a  short  conical 
socket  with  the  end  of  the  telescope  axis,  to  which  it  is 
clamped  by  a  milled  head  screw,  and  made  adjustable 
by  a  tangent  screw  and  spring  on  the  enlarged  end  of 
the  tube.  When  the  clamp  screw  is  released  the  level 
turns  vertically  upon  the  axis,  and  can  thus  be  set  at 
any  angle  with  the  telescope,  the  final  adjustment  being 
made  by  its  tangent  screw. 

The  latitude  being  set  off  upon  the  vertical  arc  as 
usual,  the  level  is  clamped  and  brought  into  the  middle, 
as  above  described. 

The  telescope  may  then  be  released  and  used  in 
running  lines,  until  it  is  desired  to  recover  the  latitude 
again.  This  is  easily  and  accurately  done  without  re- 
ferring to  the  vertical  arc. 

The  use  of  the  attachment  in  running  any  desired 
grade  is  readily  understood. 

Patented  latitude  level,  No.  193,  together  with  an  ad- 
justing level,  No.  196,  and  an  adjusting  bar,  No.  197, 
are  furnished  without  extra  charge  with  any  new  transit 
having  a  Burt  Solar  Attachment. 


106 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


FIG.  33 

No.  180 

ATTACHED    MAGNIFIER 


ATTACHED  MAGNIFIERS  OR 
MICROSCOPES  are  frequently 
used  over  the  verniers  of  the 
horizontal  or  vertical  limb,  and 
are  held  by  a  universal  three- 
jointed  arm,  which  allows  the 
lens  to  be  placed  over  any 
point  of  the  vernier.  The 
magnifier  for  the  "A"  vernier 
can  also  be  used  for  reading 
the  vernier  of  the  vertical  limb 
(any  style  having  one  vernier.) 


Attached  microscopes,  Nos.  181  and  182,  can  be 
supplied  if  desired.  See  No.  18-A  Piecise  Transit, 
page  49. 


FIG.  34 
No.  192  SOLAR  SCREEN 

SOLAR  SCREEN.  If  desired,  we  furnish  a  Solar 
Screen  arranged  to  clamp  to  the  eyepiece  end  of  the 
telescope,  and  detachable  at  will.  On  this  screen  the 
image  of  the  sun  and  cross  wires  can  be  readily  observed, 
a  greater  focusing  movement  of  the  eyepiece,  however, 
being  required. 


TRANSIT  INSTRUMENTS  107 

ASTRONOMICAL  TERMS 

IN  the  following  pages  we  define  the  terms  employed 
in  the  use  and  adjustment  of  the  Solar  Attachment, 
which  may  be  helpful  to  one  not  familiar  with  solar 
instruments.  (See  Fig.  35). 

SUN.  The  sun  is  the  fixed  center  of  the  solar  sys- 
tem, although  for  convenience  it  is  often  spoken  of  as 
in  motion  around  the  earth. 

EARTH.  The  earth  makes  a  complete  revolution 
around  the  sun  in  three  hundred  and  sixty-five  days, 
five  hours,  forty-eight  minutes,  and  forty-six  seconds. 
It  also  rotates  about  an  imaginary  line  passing  through 
its  center,  termed  its  axis,  once  in  twenty-three 
hours,  fifty-six  minutes,  and  four  seconds,  mean  time, 
turning  from  west  to  east. 

POLES.  The  poles  are  the  extremities  of  the  axis. 
That  in  our  hemisphere,  known  as  the  north  pole,  if 
produced  indefinitely  toward  the  heavens,  would  reach 
a  point  near  the  polar  star,  called  the  north  pole  of 
the  heavens. 

EQUATOR.  The  equator  is  an  imaginary  line  passing 
around  the  earth,  equidistant  from  the  poles,  and  in 
a  plane  at  right  angles  with  the  axis.  If  the  plane  of 
the  equator  were  produced  to  the  heavens,  it  would 
form  what  is  called  the  celestial  equator. 

ORBIT.  The  orbit  of  the  earth  is  the  path  in  which 
it  moves  in  its  yearly  revolution.  If  the  plane  of  this 
orbit  were  produced  to  the  heavens,  it  would  form  the 
ecliptic,  or  the  sun's  apparent  path  in  the  heavens. 


108         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  earth's  axis  is  inclined  to  its  orbit  at  an  angle  of 
about  23°  27',  making  an  angle  of  the  same  degree  be- 
tween the  earth's  orbit  and  its  equator  or  between  the 
celestial  equator  and  the  ecliptic. 

EQUINOXES.  The  equinoxes  are  the  two  points  at 
which  the  ecliptic  and  the  celestial  equator  intersect  one 
another. 

DECLINATION  OF  THE  SUN.  The  declination  of  the 
sun  is  its  angular  distance  north  or  south  of  the  celestial 
equator.  When  the  sun  is  at  the  equinoxes,  about  the 
21st  of  March  and  the  21st  of  September  of  each  year, 
its  declination  is  0,  or  it  is  said  to  be  on  the  equator. 
From  these  points  its  declination  gradually  increases, 
until  on  the  21st  of  June  and  the  21st  of  December  it  is 
23°  27'  distant  from  the  equator. 

It  is  the  declination  which  causes  the  sun  to  appear 
so  much  higher  in  summer  than  in  winter,  its  altitude  in 
the  heavens  being  about  46°  54/  more  on  the  21st  of 
June  than  it  is  on  the  21st  of  December. 

HORIZON.  The  horizon  of  a  place  is  the  visible 
boundary  of  a  plane,  tangent  to  the  earth  at  that  place, 
or  at  right  angles  to  a  vertical  line.  The  horizon,  or  a 
horizontal  surface,  is  determined  by  the  surface  of  a 
liquid  at  rest,  or  by  the  spirit  levels  of  an  instrument. 

ZENITH.  The  zenith  of  a  place  is  the  point  directly 
overhead,  in  a  line  at  right  angles  with  the  horizon. 

MERIDIAN.  The  meridian  circle  of  a  place  is  a  great 
circle  passing  through  the  zenith  of  that  place  and  the 
poles  of  the  earth. 


TRANSIT  INSTRUMENTS  109 

The  meridian,  or  true  north  and  south  line,  is  the 
line  determined  by  the  intersection  of  the  plane  of  the 
meridian  circle  with  the  plane  of  the  horizon. 

MERIDIAN  ALTITUDE.  The  meridian  altitude  of  the 
sun  is  its  angular  elevation  above  the  horizon  when 
passing  the  meridian  of  the  place,  and  is  equal  to  the 
co-latitude  plus  the  declination. 

LATITUDE.  The  latitude  of  a  place  is  its  angular 
distance  north  or  south  of  the  equator,  measured  on  the 
meridian.  At  the  equator  the  latitude  is  0°,  and  at  the 
poles  90°.  The  co-latitude  of  a  place  is  its  angular  dis- 
tance from  the  nearest  pole,  and  is  equal  to  90°  minus 
the  latitude. 

LONGITUDE.  The  longitude  of  a  place  is  its  angular 
distance  east  or  west  of  a  given  place  taken  as  the 
starting  point,  or  first  meridian.  It  is  measured  on  the 
equator  or  on  any  parallel  of  latitude. 

In  the  Nautical  Almanac,  which  is  commonly  used 
with  a  solar  instrument,  the  longitude  of  the  principal 
places  in  the  United  States  is  reckoned  from  Greenwich, 
England,  and  expressed  both  in  degrees  and  hours. 

ZENITH  DISTANCE.  The  zenith  distance  of  any 
heavenly  body  is  its  angular  distance  north  or  south  of 
the  zenith  of  a  place,  measured  when  the  body  is  on  the 
meridian.  The  zenith  distance  of  the  north  pole  is 
equal  to  the  co-latitude. 

Suppose  a  person  to  be  on  the  equator  at  the  time  of 
an  equinox;  the  sun,  when  on  the  meridian,  would  be  in 
the  zenith  of  the  place,  and  the  poles  of  the  earth  would 
lie  in  a  horizontal  line. 


110         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Disregarding,  for  the  present,  the  declination  of  the 
sun,  let  us  suppose  that  the  person  travels  toward  the 
north  pole.  As  he  passes  to  the  north,  the  sun  will 
descend  from  the  zenith,  and  the  pole  will  rise  from  the 
horizon  in  the  same  proportion,  until  when  he  arrives 
at  the  north  pole  of  the  earth  the  sun  will  have  declined 
to  the  horizon,  and  the  pole  of  the  heavens  will  have 
reached  the  zenith. 

The  altitude  of  the  pole  at  any  place,  or  the  distance 
of  the  sun  from  the  zenith,  would,  in  the  case  supposed, 
give  the  observer  the  latitude  of  that  place. 

If  we  now  take  into  account  the  sun's  declination,  it 
will  increase  or  diminish  its  meridian  altitude,  according 
as  it  passes  north  or  south  of  the  equator ;  but  the  declin- 
ation of  the  sun  at  any  time  being  known,  its  zenith 
distance,  and  therefore  the  latitude  of  the  place,  can  be 
readily  ascertained  by  an  observation  made  when  the 
sun  is  on  the  meridian.  It  is  by  this  method  that  we 
obtain  the  latitude  of  any  place  by  the  Solar  Attach- 
ment. 

TIME.  A  solar  day  is  the  interval  of  time  between 
the  departure  of  the  sun  from  the  meridian  of  a  place 
and  its  succeeding  return  to  the  same  position.  The 
length  of  the  solar  day,  by  reason  of  the  inclination  of 
the  earth's  axis,  is  constantly  changing. 

MEAN  SOLAR  DAY.  In  order  to  have  a  uniform 
measure  of  time,  we  have  recourse  to  what  is  termed  a 
mean  solar  day,  the  length  of  which  is  equal  to  the  mean 
or  average  of  all  the  solar  days  in  a  year. 


TRANSIT  INSTRUMENTS  111 

MEAN  SOLAR  TIME.  The  time  thus  given  is  called 
mean  solar  time,  and  is  the  same  at  any  instant  for  all 
points  on  the  same  meridian,  differing,  however,  at 
points  on  different  meridians. 

STANDARD  TIME.  Since  November,  1883,  in  the 
United  States,  the  mean  solar  times  of  the  meridians 
60°,  75°,  90°,  and  120°  west  of  Greenwich  are  adopted 
as  standard  time,  and  are  called  respectively  Colonial, 
Eastern,  Central,  Mountain,  and  Pacific  time.  The  time 
of  each  place  differs  from  that  of  the  next  by  one  hour. 
Instead  of  employing  the  local  mean  solar  time,  the 
time  used  is  the  mean  solar  time  at  the  nearest  of  the 
standard  meridians. 

At  Troy,  N.  Y.,  the  longitude  is  73°  40'  west,  or 
four  hours,  fifty-four  minutes  and  forty  seconds;  hence 
the  mean  solar  time  is  five  minutes  and  twenty  seconds 
more  than  the  standard  time.  At  Minneapolis  the  long- 
itude is  six  hours,  twelve  minutes  and  fifty-seven 
seconds;  hence  the  mean  solar  time  is  twelve  minutes 
and  fifty-seven  seconds  less  than  standard  time,  since 
the  city  is  west  of  the  meridian. 

EQUATION  OF  TIME.  The  sun  is  sometimes  faster 
and  sometimes  slower  than  the  clock,  the  difference  being 
called  the  equation  of  time.  It  gives  the  difference 
between  the  solar  day  and  the  mean  solar  day. 

APPARENT  NOON.  The  moment  when  the  sun  is  on 
the  meridian  of  any  place  is  called  apparent  noon,  and 
this  being  ascertained,  we  can,  by  adding  the  equation 
of  time  for  the  given  day  to,  or  subtracting  it  from, 
apparent  noon,  according  as  the  sun  is  slow  or  fast, 


112         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

obtain  the  time  of  mean  noon,  which,  converted  to  stan- 
dard time,  is  used  to  set  the  watch. 

DIFFERENCE  OF  LONGITUDE.  As  the  earth  makes  a 
complete  rotation  upon  its  axis  once  a  day,  every  point 
on  its  surface  must  pass  through  three  hundred  and  sixty 
degrees  in  twenty-four  hours,  or  fifteen  degrees  in  one 
hour,  and  so  on  in  the  same  ratio.  As  the  rotation  is 
west  to  east,  the  sun  would  come  to  the  meridian  of  every 
place  fifteen  degrees  west  of  Greenwich  just  one  hour 
later  than  the  time  given  in  the  Ephemeris  for  apparent 
noon  at  Greenwich. 

To  an  observer  at  Troy,  N.  Y.,  the  longitude  of 
which  is,  in  time,  four  hours,  fifty-four  minutes,  forty 
seconds,  the  sun  would  come  to  the  meridian  nearly  five 
hours  later  than  at  Greenwich,  and  thus,  when  it  is  12 
M.  at  that  place  it  is  only  about  7  A.  M.  in  Troy. 

REFRACTION.  By  reason  of  the  atmosphere,  the 
rays  of  light  from  the  sun  are  bent  out  of  their  course, 
so  as  to  make  its  altitude  appear  greater  than  is  actually 
the  case. 

The  refraction  varies  according  to  the  altitude  of  the 
body  observed,  being  zero  when  it  is  in  the  zenith,  about 
one  minute  when  midway  from  the  zenith  to  the  horizon, 
and  almost  thirty-four  minutes  when  in  the  horizon. 
The  proper  allowance  to  be  made  for  refraction  in 
setting  off  the  declination  is  fully  explained  on  pages 
125  to  131. 

EFFECT  OF  REFRACTION.  If  the  latitude  and  decim- 
ation of  the  sun  were  both  zero,  the  position  of  the  sun 
at  noon  would  be  at  the  zenith  and  there  would  be  no 


TRANSIT  INSTRUMENTS  113 

refraction.  At  any  other  latitude,  declination  or  hour, 
the  apparent  position  of  the  sun  would  be  lower  and 
refraction  must  be  taken  into  account. 

Again,  the  angles  which  the  equatorial  lines  of  the 
Solar  Attachments  make  with  the  horizontal  are  con- 
tinually changing,  as  the  declination  arm  is  made  to 
follow  the  course  of  the  sun  during  an  entire  day.  Thus 
in  the  morning  and  evening  the  equatorial  lines  are  more 
or  less  inclined  to  the  horizon,  while  at  noon  they  are 
parallel  with  it.  It  follows  that  the  excess  of  refraction 
at  morning  and  evening  is  in  some  measure  balanced  by 
the  fact  that  the  position  of  the  sun's  image  with  refer- 
ence to  the  equatorial  lines  is  then  less  affected  by  it, 
on  account  of  the  greater  inclination  of  the  lines  to  the 
horizon. 


114         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

BURT   SOLAR  ATTACHMENT 

THE  solar  attachment  is  essentially  the  solar  appara- 
tus of  William  A.  Burt,  placed  upon  the  cross  bar 
of  the  ordinary  transit.     A  disk  one  and  one-half 
inches  in  diameter,  having  a  short,  round  pivot  project- 
ing above  its  upper  surface,  is  screwed  to  the  telescope 
axis.     Upon  this  pivot  rests  the  enlarged    base    of    the 
polar  axis,  which  is  firmly  connected  with  the  disk  by 
four  capstan  head  screws  passing  from  the  under  side 
of  the  disk  into  the  base.     These  screws  serve  to  adjust 
the  polar  axis,  as  will  be  explained  hereinafter. 

HOUR  CIRCLE.  The  hour  circle  surrounding  the  base 
of  the  polar  axis  is  easily  movable  about  it,  and  can  be 
fastened  at  any  point  desired  by  two  flat  head  screws 
above.  It  is  graduated  to  five  minutes  of  time,  is  figured 
from  I  to  XII,  and  is  read  by  an  index  fixed  to  the  dec- 
lination arc  and  moving  with  it.  A  hollow  cone  or 
socket,  fitting  the  polar  axis  and  made  to  move  upon  it, 
or  to  be  clamped  at  any  point  desired  by  a  milled  head 
screw  on  top,  furnishes  by  its  arms  below  a  firm  sup- 
port for  the  declination  arc,  which  is  fastened  to  it. 

DECLINATION  ARC.  The  declination  arc  has  a  radius 
of  five  inches,  is  graduated  to  quarter  degrees,  and  reads 
by  vernier  to  single  minutes.  The  declination  arc  has 
the  usual  lenses  and  silver  plate  on  the  two  opposite 
blocks,  also  a  clamp  and  tangent  movement,  as  shown  in 
the  illustration.  The  arc  of  the  declination  limb  is 
turned  on  its  axis  and  one  or  the  other  solar  lens  is  used, 
as  the  sun  is  north  or  south  of  the  equator.  The  illus- 
tration shows  its  position  when  the  sun  is  north. 


TRANSIT  INSTRUMENTS 


115 


LATITUDE  ARC.  The  latitude  is  set  off  by  means  of 
a  large  vertical  limb  figured  from  the  center  each  way 
in  two  rows,  from  0  to  80  degrees  and  from  90  to  10 
degrees,  the  first  series  being  intended  for  reading  ver- 
tical angles,  and  the  second  series  for  setting  off  the 


FIG.  35 
No.  190  BURT  SOLAR  ATTACHMENT 

latitude.  The  vernier  of  the  vertical  limb  is  made 
movable  by  the  tangent  screw  so  attached  that  its  zero 
and  that  of  the  limb  are  readily  made  to  coincide  when, 
in  adjusting  the  limb  to  the  level  of  the  telescope,  the 
arc  is  clamped  to  the  axis. 


116        W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  usual  tangent  movement  to  the  telescope  axis 
serves  to  incline  the  telescope  to  the  proper  angle,  as 
described.  A  level  on  the  under  side  of  the  telescope, 
with  ground  and  graduated  vial  is  indispensable  in  the 
use  of  the  solar  attachment.  The  arcs,  verniers,  and 
hour  circle  are  all  graduated  on  sterling  silver. 

EXPLANATION  OF  THE  BURT  SOLAR  ATTACHMENT. 
When  the  telescope  is  set  horizontal  by  its  spirit  level, 
the  hour  circle  will  be  in  the  plane  of  the  horizon,  (see 
Fig.  36),  the  polar  axis  will  point  to  the  zenith,  and  the 
zeros  of  the  vertical  arc  and  its  vernier  will  coincide. 
If  we  incline  the  telescope,  directed  north,  the  polar 
axis  will  descend  from  the  direction  of  the  zenith.  The 
sun's  polar  distance,  or  the  co-latitude  of  the  place,  can 
be  laid  off  on  the  vertical  arc — the  latitude  itself  being 
found  by  subtracting  this  amount  from  90  degrees,  or 
by  reading  the  inner  row  of  figures,  which  amounts  to 
the  same  thing. 

When  the  sun  passes  above  or  below  the  equator,  its 
declination,  or  angular  distance  from  it,  as  given  in  the 
Ephemeris,  can  be  set  off  upon  the  declination  arc,  and 
its  image  brought  into  position  as  before. 

In  order  to  do  this,  however,  it  is  necessary  not  only 
that  the  latitude  and  declination  be  correctly  set  off  upon 
their  respective  arcs,  but  also  that  the  instrument  be 
moved  in  azimuth  until  the  polar  axis  points  to  the  pole 
of  the  heavens,  or,  in  other  words,  is  placed  in  the  plane 
of  the  meridian.  Thus  the  position  of  the  sun's  image 
will  indicate  not  only  the  latitude  of  the  place,  the  dec- 
lination of  the  sun  for  the  given  hour,  and  the  apparent 


TRANSIT  INSTRUMENTS  117 

time,  but  it  will  also  determine  the  meridian,  or  true 
north  and  south  line  passing  through  the  place  where 
the  observation  is  made. 

The  interval  between  two  equa- 
torial lines,  as  well  as  between  the 
hour  lines  on  the  silvered  blocks,  is 
just  sufficient  to  include  the  circular 
image  of  the  sun,  as  formed  by  the  solar  lens  on  the 
opposite  end  of  the  revolving  arm. 

DECLINATION.  Allowance  for  declination:  Let  us 
now  suppose  the  observation  made  when  the  sun  has 
passed  the  equinoctial  point,  and  when  its  position  is 
affected  by  declination. 

By  referring  to  the  Ephemeris,  and  setting  off  on 
the  arc  the  declination  for  the  given  day  and  hour,  we 
are  still  able  to  determine  its  position  with  the  same 
certainty  as  if  it  remained  on  the  equator. 

When  the  solar  attachment  is  accurately  adjusted 
and  the  transit  plates  precisely  horizontal,  the  latitude 
of  the  place  and  the  declination  of  the  sun  for  the  given 
day  and  hour  being  set  off  on  their  respective  arcs,  and 
the  instrument  set  approximately  north  by  the  magnetic 
needle,  the  image  of  the  sun  cannot  be  brought  between 
the  equatorial  lines  until  the  polar  axis  is  placed  in  the 
plane  of  the  meridian  of  the  place,  or  in  a  position  par- 
allel with  the  axis  of  the  earth.  The  slightest  deviation 
from  this  position  will  cause  the  image  to  pass  above  or 
below  the  lines,  and  thus  the  error  will  be  detected. 

From  the  position  of  the  sun  in  the  solar  system  we 
thus  obtain  a  direction  absolutely  unchangeable,  from 
which  to  run  lines  and  measure  horizontal  angles. 


118         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

This  simple  principle  is  not  only  the  basis  of  the 
construction  of  solar  instruments,  but  it  is  the  sole  cause 
of  their  superiority  over  instruments  having  only  the 
magnetic  needle.  For  in  an  instrument  having  a  mag- 
netic needle,  the  accuracy  of  the  horizontal  angles 
indicated,  and  therefore  of  all  the  observations  made, 
depends  upon  the  delicacy  of  the  needle  and  the  con- 
stancy with  which  it  assumes  a  certain  direction,  called 
the  magnetic  meridian. 

ADVANTAGES  OF  THE  BURT  SOLAR  ATTACHMENT. 
The  attachment  can  be  added  to  the  telescope  of  any 
good  transit  at  a  comparatively  small  expense,  thus 
enabling  the  surveyor  to  establish  the  true  meridian,  to 
determine  the  correct  latitude,  and  to  obtain  true  time 
approximately. 

Its  adaptation  to  the  purposes  of  illustration  and 
instruction  in  practical  astronomy  in  colleges  and  schools 
will  occur  to  every  teacher;  and  it  furnishes  for  the 
surveyor  a  long  sought  and  much  needed  instrument. 

When  not  in  use  the  attachment  should  be  removed 
from  the  telescope  and  packed  in  the  instrument  box, 
and  the  thin  shield  put  on  the  polar  axis  and  kept  in  its 
place  by  the  screw  and  washer  of  the  socket. 

It  is  evident  that  all  transits  to  which  the  solar 
attachment  is  to  be  added  should  have  a  horizontal  limb 
and  verniers,  and  should  be  furnished  with  a  level  on 
telescope,  clamp  and  tangent  to  telescope  axis,  and  a 
vertical  arc  and  vernier.  They  should  also  have  a  mov- 
able compass  circle  to  set  off  the  magnetic  declination, 
and  should  be  leveled  by  leveling  screws.  They  must 


TRANSIT  INSTRUMENTS 


119 


FIG.   36 

No.  30-A  PRECISE  TRANSIT 

WITH  BURT  SOLAR  ATTACHMENT 

ILLUSTRATION  ALSO  SHOWS  BEAMAN  STADIA  ARC 


120        W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

be  in  perfect  order,  especially  in  respect  to  the  sockets, 
before  correct  work  can  be  done. 

CARE  OF  THE  BURT  SOLAR  ATTACHMENT.  The  Solar 
Attachment  can  be  used  with  satisfactory  results  only 
on  a  transit  which  is  in  good  repair  and  adjustment. 
The  errors  arising  from  defects  either  in  worn  or  dam- 
aged bearings  or  imperfect  adjustment  have  a  direct 
effect  on  the  Solar  Attachment. 

The  principal  sources  of  error  in  the  transit  are 
found  in  damaged  plates  or  centers,  loose  centers,  or 
irregular  or  loose  bearings  of  the  telescopic  axis.  The 
latter  is  the  most  frequent,  and  effects  the  setting  of 
the  latitude  by  describing  an  elipse  instead  of  a  true  arc. 

The  transit  must  be  kept  clean  at  all  times,  the  polar 
axis  covered  with  the  shield  provided  for  the  purpose 
when  the  Solar  is  not  in  use,  and  the  tapered  bearing 
and  seat,  as  well  as  the  socket  of  the  Attachment, 
thoroughly  cleaned  with  a  soft  cloth  before  using. 

By  taking  the  precautions  mentioned  and  barring 
accidents,  the  Solar  will  remain  in  perfect  order  and 
adjustment  indefinitely. 

To  ADJUST  THE  BURT  SOLAR  ATTACHMENT 

To  adjust  the  Burt  Solar  Attachment,  proceed  as 
follows :  ._ 

SOLAR  LENSES  AND  LINES.  Detach  the  declination 
arm  by  taking  off  the  clamp  and  tangent  screws,  and 
remove  the  center  by  which  the  arm  is  pivoted  on  the  arc. 

Substitute  for  the  declination  arm  upon  the  attach- 
ment the  adjusting  bar  furnished  with  every  solar 


TRANSIT  INSTRUMENTS  121 

instrument.  The  center  of  the  declination  arm  fitting 
into  the  hole  at  one  end  of  the  bar,  and  the  bar  being 
further  secured  to  the  attachment  by  the  clamp  screw 
passing  through  the  hole  in  the  declination  arc  left  by  the 
removal  of  the  tangent  screw,  into  the  threaded  hole  at 
the  other  end  of  the  adjusting  bar,  thus  forms  a  sup- 
port upon  which  the  declination  arm  can  be  adjusted. 

Place  the  declination  arm  on  the  adjuster,  turn  one 
end  to  the  sun,  and  bring  it  into  such  a  position  that  the 
image  of  the  sun  is  made  to  appear  precisely  between 
the  equatorial  lines  on  the  opposite  plate. 

Carefully  turn  the  arm  over,  until  it  rests  upon  the 
adjuster  by  the  opposite  faces  of  the  rectangular  blocks, 
and  again  observe  the  sun's  image.  If  it  remains  be- 
tween the  lines  as  before,  the  arm  is  in  adjustment.  If 
not,  loosen  the  three  small  screws  and  move  the  silver 
plate  under  their  heads  until  one  half  the  error  in  the 
position  of  the  sun's  image  is  removed. 

Bring  the  image  again  between  the  lines,  and  repeat 
the  operation  as  above  on  both  ends  of  the  arm,  until  the 
image  will  remain  between  the  lines  of  the  plate  in  both 
positions  of  the  arm,  when  it  will  be  in  proper  adjust- 
ment, and  the  arm  may  be  replaced  in  its  former  position 
on  the  attachment.  This  adjustment  is  very  rarely 
needed  in  our  instruments,  the  lenses  being  cemented  in 
their  cells  and  the  plates  securely  fastened. 

To  ADJUST  THE  VERNIER  OF  THE  DECLINATION  ARC. 
Set  the  vernier  at  zero,  and  raise  or  lower  the  telescope 
until  the  sun's  image  appears  exactly  between  the 
equatorial  lines. 


122         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Having  the  telescope  axis  clamped,  carefully  revolve 
the  arm  until  the  image  appears  on  the  other  plate.  If 
precisely  between  the  lines,  the  adjustment  is  complete. 
If  not,  move  the  declination  arm  by  its  tangent  screw 
until  the  image  wrill  come  precisely  between  the  lines  on 
the  two  opposite  plates.  Clamp  the  arm  and  remove  the 
index  error  by  loosening  two  screws  that  fasten  the  ver- 
nier; place  the  zeros  of  the  vernier  and  limb  in  exact 
coincidence,  tighten  the  screws,  and  the  adjustment  is 
complete. 

To  ADJUST  THE  POLAR  Axis.  Level  the  instrument 
carefully  by  the  long  level  of  the  telescope,  using  the 
tangent  movement  of  the  telescope  axis  in  connection 
with  the  leveling  screws,  until  the  bubble  will  remain  in 
the  middle  during  a  complete  revolution  of  the  instru- 
ment upon  its  axis. 

Place  the  solar  attachment  upon  the  axis  and  see 
that  it  moves  easily  around  it.  Bring  the  declination 
arm  into  the  same  vertical  plane  with  the  telescope, 
place  the  Adjusting  Level,  No.  196,  upon  the  top  of  the 
rectangular  blocks,  and  bring  the  bubble  of  the  level 
into  the  middle  by  the  tangent  screw  of  the  declination 
arc. 


TRANSIT  INSTRUMENTS 


123 


FIG.  37 
No.  196  STRIDING  OR  ADJUSTING  LEVEL 

Turn  the  arc  half  way  around,  bringing  it  again 
parallel  with  the  telescope,  and  note  the  position  of  the 
level.  If  in  the  middle,  the  polar  axis  is  vertical  in  that 
direction.  If  not  in  the  middle,  correct  one  half  the 
error  by  the  capstan  head  adjusting  screws  under  the 
base  of  the  polar  axis,  moving  each  screw  of  the  pair 
the  same  amount,  but  in  an  opposite  direction.  Bring 
the  level  to  the  middle  again  by  the  tangent  screw  of 
the  declination  arc,  and  repeat  the  operation  as  before, 
until  the  bubble  will  remain  in  the  middle  when  the 
adjusting  level  is  reversed. 


124         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Pursue  the  same  course  in  adjusting  the  arc  in  the 
second  position,  or  over  the  telescope  axis,  and  when 
completed  the  level  will  remain  in  the  middle  during  an 
entire  revolution  of  the  arc,  showing  that  the  polar  axis 
is  at  right  angles  with  the  level  under  the  telescope, 
or  truly  vertical. 

As  this  is  by  far  the  most  delicate  and  important 
adjustment  of  the  solar  attachment,  it  should  be  made 
with  the  greatest  care,  the  bubble  being  kept  precisely 
in  the  middle  and  frequently  inspected  Li  the  course  of 
the  adjustment. 

The  adjusting  level  itself  can  be  easily  corrected, 
if  necessary,  by  the  screw  at  one  end,  when  reversed 
upon  a  plane  surface,  exactly  as  a  mason's  level  is 
adjusted. 

To  ADJUST  THE  HOUR  ARC.  Whenever  the  instru- 
ment is  set  in  the  meridian,  as  will  be  hereafter  describ- 
ed, the  index  of  the  hour  arc  should  read  apparent  time. 
If  not,  loosen  the  two  flat  head  screws  on  the  top  of  the 
hour  circle,  and  with  the  hand  turn  the  circle  around 
until  the  proper  reading  is  indicated,  fasten  the  screws 
again,  and  the  adjustment  will  be  complete. 

To  USE  THE  BURT  SOLAR  ATTACHMENT 

1.  Compute  the  sun's   declination  for  the  day  and 
the  hours  when  observations  are  to  be  made,  as  shown 
in  the  examples  on  pages  132  to  134. 

2.  Set  the  declination  arc  for  the  hour  as  computed. 

3.  Carefully  level  the  transit,  using  the  long  tele- 
scope level  for  precision. 


TRANSIT  INSTRUMENTS  125 

4.  Set  the  latitude  of  the  place  on  the  vertical  circle 
or  arc,  and  the  zeros  of  the  horizontal  limb  and  south 
vernier  in  coincidence.  All  motions  are  now  clamped. 

Release  the  lower  socket  motion  and  turn  the  transit 
until  the  sun's  image  is  precisely  between  the  horizontal 
lines,  using  the  lower  tangent  screw. 

The  instrument  will  then  be  in  the  true  meridian, 
and  an  angle  read  by  the  verniers  is  the  angle  from  the 
meridian. 

NOTE  1.  During  north  declination,  or  between  the 
months  of  March  and  September,  the  graduated  arc  end 
of  the  Solar  Attachment  is  pointed  toward  the  sun. 
During  the  other  one-half  of  the  year,  the  opposite  end 
is  toward  the  sun. 

NOTE  2.  The  greater  the  care  exercised  in  setting 
the  declination  and  latitude  and  the  leveling  of  the 
instrument,  the  better  will  be  the  results  obtained. 

Observations  may  be  made  with  the  telescope  pointed 
north,  objective  end  depressed;  again  with  the  telescope 
pointed  south,  eye  end  depressed;  or  again  with  the 
telescope  reversed  and  the  attachment  on  the  other 
side — two  other  observations.  Thus  with  four  distinct 
observations,  the  mean  may  be  taken  and  any  errors  of 
adjustment  eliminated. 

REFRACTION  IN  DECLINATION.  The  Table  of  Re- 
fractions on  pages  127  to  131  is  calculated  for  latitudes 
between  2l/2°  and  70°,  at  intervals  of  2l/2°,  that  being 
as  near  as  is  required. 

The  declination  ranges  from  0°  to  20°  both  north 
and  south,  the  -|-  declinations  being  north  and  the  — 


126         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

south,  and  is  given  for  every  5°,  that  being  sufficiently 
near  for  all  practical  purposes.  The  hour  angle  in  the 
first  column  indicates  the  distance  of  the  sun  from  the 
meridian  in  hours,  the  refraction  given  for  0  hours  being 
that  which  affects  the  observed  declination  of  the  sun 
when  on  the  meridian,  commonly  known  as  meridional 
refraction.  The  refraction  for  the  hour  just  before  or 
after  noon  is  so  nearly  that  of  the  meridian  that  it  may 
be  called  and  allowed  as  the  same. 

When  the  table  is  used,  it  must  be  remembered  that 
when  the  declination  is  north  the  algebraic  sign  in  the 
table  is  plus,  when  it  is  south  the  algebraic  sign  is  minus, 
and  the  declination  is  always  added  algebraically.  It  will 
be  noticed  that  the  refraction  in  south,  or  — ,  declination 
increases  very  rapidly  as  the  sun  nears  the  horizon, 
showing  that  observations  should  not  be  taken  with  the 
sun  when  it  is  south  of  the  equator,  less  than  one  hour 
from  the  horizon. 

THE  SOLAR  EPHEMERIS  is  published  annually.  It  is 
an  abridgment  of  the  Nautical  Almanac,  issued  by  the 
United  States  Government,  and  contains  a  Table  of 
Mean  Refractions  in  Declination  and  Tables  of  Times 
of  Elongation,  Culmination  and  Azimuths  of  Polaris. 
It  can  be  conveniently  carried  in  the  vest  pocket.  A 
copy  will  be  sent  postpaid  to  any  engineer  or  surveyor, 
upon  request. 


TRANSIT  INSTRUMENTS 


127 


TABLE  OF  MEAN  REFRACTIONS  IN 
DECLINATION 

To  apply  on  the  declination  arc  of  the  Solar  Attach- 
ment of  either  compasses  or  transits. 

Computed  by  Edward  W.  Arms,  C.  E.,  for  W.  &  L.  E.  Gurley,  Troy,  N.  Y. 


DECLINATIONS 


11 

For    Latitude    2°    30' 

+20° 

+15- 

+10° 

+5° 

0° 

—  5° 

—10° 

—15° 

—20° 

0  h. 

—18" 

—  12" 

—07" 

—02" 

+02" 

07" 

12" 

18" 

23" 

2 

—18 

—12 

—07 

—02 

+02 

07 

12 

18 

23 

3 

—17 

—11 

—06 

—01 

+03 

08 

13 

19 

25 

4 

—15 

—10 

—05 

0 

+05 

10 

15 

21 

27 

5 

—  10 

—05 

0 

+05 

10 

15 

20 

26 

32 

For  Latitude  5" 


0  h. 

—15" 

—10" 

—05" 

0" 

+05" 

10" 

15" 

20" 

27" 

2 

—15 

—10 

—05 

0 

+05 

10 

15 

20 

27 

3 

—13 

—08 

—03 

+02 

07 

12 

17 

23 

29 

4 

—10 

—05 

0 

+05 

10 

15 

20 

27 

32 

5 

—05 

0 

+05 

10 

15 

20 

27 

32 

40 

For  Latitude  7°  30' 


0  h. 

—13" 

—08" 

—02" 

+02" 

08" 

13" 

18" 

24" 

29" 

2 

—12 

—07 

—01 

+03 

09 

14 

19 

25 

31 

3 

—10 

—05 

0 

+06 

10 

15 

20 

26 

32 

4 

—05 

0 

+05 

10 

15 

20 

26 

32 

39 

5 

+07 

12 

17 

23 

29 

36 

43 

51 

I'Ol 

For  Latitude  10° 


0  h. 

—10" 

—05" 

0" 

+05" 

10" 

15" 

20" 

26" 

32" 

—07 

—03 

+02 

07 

12 

17 

22 

28 

34 

3 

—05 

0 

+03 

08 

13 

19 

25 

31 

38 

4 

0 

05 

10 

15 

20 

26 

32 

39 

46 

5 

+  15 

20 

26 

32 

39 

46 

55 

1'06 

1'19 

For  Latitude  12°  30' 


0  h. 

—08" 

—02" 

+02" 

08" 

13" 

18" 

24" 

30" 

36" 

2 

—06 

00 

+05 

10 

15 

20 

26 

32 

39 

3 

+02 

07 

12 

17 

23 

29 

36 

43 

51 

4 

'  04 

09 

14 

20 

25 

31 

40 

48 

55 

5 

21 

27 

33 

40 

48 

57 

1'08 

1'23 

1'41 

128 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


TABLE  OF  MEAN  REFRACTIONS  IN  DECLINATION 


HOUR 
ANGLE 

DECLINATIONS 

For  Latitude  15° 

+20° 

+15° 

+  10° 

+5° 

0° 

—5° 

—10° 

—  15° 

—20° 

0  h. 
2 
3 

4 

5 

—05" 
—03 
+01 
08 
29 

0" 
+02 
05 
12 
34 

+05" 
07 
11 
19 
41 

10" 
12 
16 
24 
49 

15" 
18 
22 
30 
59 

21" 
23 

28 
37 

no 

27" 
29 
34 
44 
1'24 

33" 
36 
41 
53 
1'43 

40" 
43 
49 
1'04 
208 

For  Latitude   17°    30' 


0  h. 

—02" 

+02" 

08" 

13" 

18" 

24" 

30" 

36" 

44" 

2 

0 

05 

10 

15 

21 

27 

33 

40 

48 

3 

+02 

10 

15 

21 

27 

33 

40 

48 

57 

4 

13 

18 

23 

29 

35 

43 

51 

I'Ol 

1'13 

5 

34 

41 

49 

58 

no 

1'23 

1'41 

206 

242 

For  Latitude 


0  h. 

0" 

05" 

10" 

15" 

21" 

27" 

33" 

40" 

48" 

2 

03 

07 

13 

18 

24 

30 

36 

44 

52 

3 

06 

13 

18 

24 

30 

36 

44 

52 

1'02 

4 

17 

22 

28 

35 

42 

50 

I'OO 

I'll 

126 

5 

39 

47 

57 

1'07 

1'20 

1'37 

200 

232 

325 

For   Latitude  22°   30' 


0  h. 

C2" 

08" 

13" 

18" 

24" 

30" 

36" 

44" 

52" 

2 

06 

11 

15 

21 

27 

33 

40 

48 

57 

3 

11 

15 

21 

27 

33 

40 

48 

57 

1'OS 

4 

20 

26 

32 

39 

46 

56 

1'07 

1'19 

137 

5 

45 

53 

1'03 

1'16 

1'31 

1'52 

221 

307 

428 

For  Latitude  25° 


0  h. 

05" 

10" 

15" 

21" 

27" 

33" 

40" 

48" 

57" 

2 

08 

14 

19 

25 

31 

38 

46 

54 

1'05 

3 

12 

18 

24 

30 

37 

44 

53 

1'04 

118 

4 

23 

29 

35 

45 

53 

1'03 

1'16 

131 

152 

5 

49 

59 

no 

1'24 

1'42 

2  07 

244 

346 

543 

For  Latitude   27°    30' 


0  h. 

08" 

13" 

18" 

24" 

3'  " 

36" 

44" 

52" 

1'02" 

2 

11 

16 

22 

28 

3-i 

41 

49 

I'OO 

1  10 

3 

17 

28 

35 

42 

50 

I'OO 

1  11 

126 

4 

28 

35 

42 

50 

I'OO 

I'll 

126 

143 

209 

5 

54 

1'05 

1'18 

1'34 

154 

224 

311 

438 

815 

For  Latitude  30° 


0  h. 

10" 

15" 

21" 

27" 

33" 

40" 

48" 

57" 

1'OS" 

2 

14 

19 

25 

31 

38 

46 

54 

I'Oo 

1  18 

3 

20 

26 

32 

39 

47 

55 

I'OO 

1  19 

136 

4 

32 

39 

46 

52 

roe 

1'19 

135 

157 

229 

5 

I'OO 

no 

1'24 

1'42 

207 

244 

346 

543 

1306 

TRANSIT  INSTRUMENTS 


129 


TABLE  OF  MEAN   REFRACTIONS  IN  DECLINATION 


*3 

DC 

ox 

W  •<* 

DECLINATIONS 

For  Latitude  32°    30' 

+20° 

+15° 

+10° 

+5° 

0° 

—5° 

—  10° 

—15° 

—20° 

1'14" 
126 
147 
254 

0  h. 

3 
4 
5 

13" 
17 
23 
35 
1'03 

18" 
22 
29 
43 
1'15 

24" 
28 
35 
51 
1'31 

30" 
35 
43 
I'Ol 
1  53 

36" 
42 
51 
1'13 
220 

44" 
50 
I'Ol 
127 
305 

52" 
I'OO 
113 
146 
4  25 

1'02" 
1  11 
128 
213 
736 

For  Latitude  35 c 


0  h. 

15" 

21" 

27" 

33" 

40" 

48" 

57" 

1'08" 

1-21" 

2 

20 

25 

32 

38 

46 

55 

1'05 

118 

1  35 

3 

26 

33 

39 

47 

56 

1'07 

121 

138 

2  00 

4 

39 

47 

56 

1'07 

1'20 

136 

159 

232 

325 

:> 

1'07 

1'20 

1'38 

200 

234 

329 

5  14 

1016 

For   Latitude  37 c 


0  h. 

18" 

24" 

30" 

36" 

44" 

52" 

1'02" 

1'14" 

1'29" 

2 

22 

28 

35 

42 

50 

I'OO 

112 

126 

145 

3 

29 

36 

43 

52 

1'02 

114 

129 

149 

216 

4 

43 

51 

I'Ol 

1'13 

127 

149 

214 

254 

405 

5 

I'll 

1'26 

144 

210 

249 

355 

6  15 

14  58 

For  Latitude  40C 


0  h. 

21" 

27" 

33" 

40" 

48" 

57" 

1'08" 

1'21" 

1'39" 

2 

25 

32 

39 

46 

52 

1'06 

119 

135 

157 

3 

33 

40 

48 

57 

1'OS 

121 

138 

202 

236 

4 

47 

55 

1'06 

1'19 

1  36 

158 

230 

321 

459 

5 

1'15 

1'31 

151 

220 

305 

425 

734 

25  18 

For  Latitude  42°    30' 


0  h. 

24" 

30" 

36" 

44" 

52" 

1'02" 

1'14" 

1'29" 

1'49" 

2 

28 

35 

39 

50 

I'OO 

112 

126 

1  45 

211 

3 

36 

43 

52 

1'02 

113 

1  29 

1  49 

217 

2  59 

4 

50 

I'OO 

I'll 

126 

144 

210 

249 

3  55 

616 

o 

1'19 

1  36 

1  58 

230 

322 

500 

924 

For  Latitude  45° 


o  h. 

27" 

33" 

40" 

48" 

57" 

1'08" 

1'21" 

1'39" 

2  '02" 

2 

32 

39 

46 

52 

1'06 

119 

1  35 

157 

229 

3 

40 

47 

56 

1'07 

121 

1  38 

200 

234 

329 

4 

54 

1'04 

1'16 

1  33 

154 

224 

311 

438 

8  15 

5 

1'23 

141 

205 

241 

340 

540 

1202 

For   Latitude   47°    30' 


0  h. 

30" 

36" 

44" 

52" 

1'02" 

1'14" 

1'29" 

1'49" 

2'18" 

2 

'    35 

42 

50 

I'OO 

112 

126 

1  45 

201 

2  51 

3 

43 

51 

I'Ol 

113 

128 

1  47 

2  15 

256 

408 

4 

56 

1'09 

123 

1  40 

2  05 

240 

339 

5  37 

11  18 

5 

1'27 

1  46 

2  12 

2  52 

401 

030 

16  19 

130 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


TABLE  OF  MEAN  REFRACTIONS  IN  DECLINATION 


HOUR 
ANGLE 

DECLINATIONS 

For  Latitude  50° 

+20° 

+15° 

+10° 

+5° 

0° 

—5° 

—10° 

1'39" 
157 
231 
418 
24  10 

—15° 

2'02" 
228 
323 
659 

—20° 

0  h. 
2 
3 
4 
5 

33" 
38 
47 
1'02 
130 

40" 
46 
56 
114 
151 

48" 
55 
1'06 
129 
219 

57" 
1'06 
119 
148 
304 

1'08" 
118 
136 
216 

422 

1'21" 
135 
158 
2  58 

728 

2'36" 
319 
502 
1947 

For  Latitude   52°    30' 


0  h. 

36" 

44" 

52" 

1'02" 

1'14" 

1'29" 

1'49" 

2  '18" 

3'05" 

2 

43 

50 

59 

111 

126 

142 

223 

249 

355 

3 

50 

I'OO 

I'll 

126 

145 

211 

251 

358 

622 

4 

1'05 

1  18 

135 

2  10 

228 

319 

453 

842 

5 

134 

156 

227 

3  16 

447 

852 

For  Latitude  55° 


0  h. 

40" 

48" 

57" 

1'08" 

1'21" 

1'39" 

2'02" 

2'36" 

3'33" 

2 

46 

55 

1'05 

118 

1  34 

156 

230 

315 

447 

3 

55 

1'06 

1  19 

135 

158 

230 

321 

4  44 

919 

4 

no 

123 

142 

206 

243 

344 

549 

12  41 

5 

137 

201 

234 

328 

515 

1018 

For   Latitude   57°   30' 


0  h. 

44" 

52" 

1'02" 

1'14" 

1'29" 

1'49" 

2'18" 

3'05" 

4'37" 

2 

50 

59 

111 

125 

143 

209 

247 

351 

604 

3 

58 

I'lO 

124 

1  42 

207 

243 

345 

550 

1247 

4 

I'll 

125 

143 

210 

2  50 

355 

614 

2024 

5 

1  41 

206 

242 

342 

546 

1226 

For  Latitude  60° 


0  h. 

48" 

57" 

1'08" 

1'21" 

1'39" 

2'02" 

2'36" 

3'33" 

5'23" 

2 

54 

1'04 

117 

133 

154 

224 

312 

438 

815 

3 

1'03 

1  15 

130 

1  51 

220 

304 

424 

731 

2444 

4 

1  18 

1  34 

156 

228 

3  18 

450 

853 

5 

145 

211 

250 

357 

621 

1532 

For  Latitude  02°  30' 


0  h. 
2 

52" 
58 

1'02" 
1  09 

1'14" 
123 

1'29" 
141 

1'50" 
206 

2'18" 
243 

3'00" 
344 

4'17" 
550 

7'  13" 
1244 

3 

1'07 

123 

138 

201 

235 

330 

516 

1024 

4 

1  23 

140 

205 

240 

340 

537 

1150 

, 

5 

148 

217 

259 

414 

703 

For  Latitude  65 


0  h. 

57" 

1'08" 

1'21" 

1'39" 

2'02" 

2'36* 

3'33" 

5'23" 

10'51" 

2 

1'03 

116 

1  31 

152 

221 

307 

428 

744 

3 

112 

127 

146 

212 

252 

402 

633 

4 

127 

147 

213 

254 

405 

640 

5 

152 

222 

308 

430 

752 

TRANSIT  INSTRUMENTS 


131 


TABLE  OF  MEAN  REFRACTIONS  IN  DECLINATION 


HOUR 
ANGLE 

DECLINATIONS 

For  Latitude  67°   30' 

+20° 

+15° 

+10° 

+5° 

0° 

—  5° 

—10° 

4'17" 
532 
834 

—  15° 

7'13" 
1128 

—20° 

0  h. 
2 
3 
4 
5 

1'02" 
108 
1  17 
132 
156 

1'14" 
122 
134 
153 

228 

1'29" 
140 
155 
223 
317 

1'50" 
203 
226 
314 
440 

2'18" 
239 
314 
435 

851 

3'00" 
337 
444 
805 

For  Latitude  70e 


0  h. 

1'08" 

1'21" 

1'39" 

2'02" 

2'36" 

3'33" 

5'23" 

10'51" 

2 

114 

129 

1  50 

218 

300 

417 

713 

3 

123 

143 

205 

241 

341 

559 

1215 

4 

137 

200 

234 

328 

520 

10  12 

5 

202 

233 

327 

511 

1005 

132         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

To  COMPUTE  THE  DECLINATION  OF  THE  SUN 

Suppose  the  corrected  declination  is  desired  for  the 
different  hours  of  May  15,,  1919,  at  Troy,  N.  Y.  The 
latitude  is  42°  44-'.  The  longitude  is  practically  five 
hours;  so  that  the  declination  given  in  the  Ephemeris 
for  apparent  noon  of  that  day  at  Greenwich  would  be 
that  for  7  A.  M.  at  Troy,  or  five  hours  earlier.  Note 
carefully  the  algebraic  signs.  The  declination  is  North 
or  plus.  Its  hourly  difference  is  plus.  The  refraction 
always  is  plus.  Hence  we  use  the  algebraic  sum: 


+18°  40'  44". 3  is    the    tabular    decimation    for  7  A.  M. 

+36". 0  difference    for    one    hour 


+18°  41'  20". 3  +  ref.    (4  hrs.)    55"  —  18°   42'   15"  8  A.  M. 

+36".0 


+18°  41'  56". 3   +  ref.    (3  hrs.)    39"  =  18°   42'   35"  9  A.  M. 

+36".0 


+18°  42'  32". 3  +  ref.    (2  hrs.)    30"  —  18°   43'   02"  10  A.  M. 

+36".0 


+  18°  43'  08". 3   +  ref.    (1   hr.  )    26"  =  18°   43'   34"  11  A.  M. 

+3G".0 


+18°  43'  44". 3   +  ref.    (0  hrs.)    26"  =  18°   44'   10"  12  Noon 

+36".0 


+18"  44'  20". 3  +  ref.    (1   hr.  )    26°   =  18°   44'   46"  1  P.   M. 

-f36".0 


+  18°  44'  50". 3  +  ref.    (2  hrs.)    30"  =  18°   45'   26"  2  P.  M. 

+  36".0 


4-18°  45'  32". 3   +  ref.    (3  hrs.)    39"  =  18°   4G'   11"  3  P.  M. 

+36".0 


+18°  46'  08". 3  4-  ref.    (4   tors.)    55"  =  18°   47'   03"  4  P.  M. 

+36".0 

+18°  46'  44". 3  +  ref.    (5   hrs.)    1'2G"   =  18°   48'    10"  5  P.  M. 


TRANSIT  INSTRUMENTS  133 

Again,  suppose  the  corrected  declination  is  desired 
for  the  different  hours  of  October  20th,  1921,  at  Troy, 
N.  Y.  Now  the  declination  and  hourly  difference  are. 
both  minus  and  the  refraction  is  plus. 


— 10°  03'  29". 2  the  tabular  declination  for  7  A.  M. 

— 54". 2  difference    for    one    hour 


—10°  04'  23". 4  +  ref.    (4  hrs.)   2'49"  —  10°  01'  34"  8  A.  M. 

—54".  2 


—10°  05'  17". 6  +  ref.    (3  hrs.)   1'49"  —  10°  03'  29"  9  A.  M. 

—54".  2 


—10°  06'  11". 8  +  ref.    (2  hrs.)   1'26"  =  10°  04'  46"  10  A.  M. 

—54".  2 


—10°  07'  06". 0  +  ref.    (1  hr.  )    1'14"  —  10°  05'  52"  11  A.  M. 

—54".  2 


—10°  08'  00". 2   +  ref.    (0  hr.  )   1'14"  =  10°   06'  46"  12  Noon 

—54".  2 


—10°  08'  54". 4  +  ref.    (1  hr.  )   1'14"  =  10°   07'   40"  1  P.  M. 

—54".  2 


—10°  09'  48". 6   +  ref.    (2  hrs.)   1'26"  —  10°   08'  23"  2  P.  M. 

—54".  2 


—10°  10'  42". 8  +  ref.    (3  hrs.)    1'49"  =  10°  08'  54"  3  P.   M. 

—54".  2 


— 10°  11'  37". 0  +  ref.    (4  hrs.)   2'49"  =  10°   08'  48"  4  P.  M. 

It  will  be  found  that  the  use  of  the  table,  as  illus- 
trated above,  will  not  only  relieve  the  surveyor  of  the 
perplexity  which  hitherto  attended  the  subject  of  refrac- 
tions, but  will  also  enable  him  to  secure  more  accurate 
results  than  by  some  other  methods  commonly  given. 


134         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  calculation  of  the  declination  for  the  different 
hours  of  the  day  should,  of  course,  be  made  and  noted 
before  the  surveyor  begins  his  work,  that  he  may  lay 
off  the  change  from  hour  to  hour,  from  a  table  prepared 
as  before  described. 

To  FIND  THE  LATITUDE 

Level  the  instrument  very  carefully,  using  the  tele- 
scope level,  until  the  bubble  will  remain  in  the  middle 
during  a  complete  revolution  of  the  instrument,  the 
tangent  movement  of  the  telescope  being  used  in  con- 
nection with  the  leveling  screws,  and  the  axis  of  the 
telescope  being  clamped. 

Clamp  the  vertical  arc,  so  that  its  zero  and  the  zero 
of  its  vernier  coincide  as  near  as  may  be,  and  bring  them 
into  exact  line  by  the  tangent  screw  of  the  vernier. 

Set  off  on  the  proper  arc  the  declination  of  the 
sun  for  apparent  noon  of  the  given  day,  corrected  for 
the  meridional  refraction.  Note  the  equation  of  time, 
and  fifteen  or  twenty  minutes  before  noon  direct  the 
telescope  to  the  north  and  lower  the  objective  end  until 
the  sun's  image  can  be  brought  nearly  into  position  be- 
tween the  equatorial  lines,  by  moving  the  instrument 
upon  its  spindle  and  the  declination  arc  from  side  to 
side. 

The  declination  arc  being  brought  directly  in  line 
with  the  telescope,  clamp  the  axis,  and  with  the  tangent 
screw  of  the  telescope  axis  bring  the  image  precisely 
between  the  lines,  following  the  sun's  motion  as  the 
image  runs  below  the  lower  equatorial  line,  or,  in  other 
words,  as  long  as  the  sun  continues  to  rise  in  the  heavens. 


TRANSIT  INSTRUMENTS  135 

When  the  sun  reaches  the  meridian  the  image  will 
remain  stationary  in  altitude  for  an  instant,  and  will 
then  begin  to  rise  on  the  plate. 

The  moment  the  image  ceases  to  run  below  is  appar- 
ent noon,  when  the  index  of  the  hour  arc  should  indicate 
XII,  and  the  latitude  be  determined  by  the  reading  of 
the  vertical  arc. 

The  angle  through  which  the  polar  axis  has  moved 
in  the  operation  just  described  is  measured  from  the 
zenith  instead  of  the  horizon,  so  that  the  angle  read  on 
the  vertical  limb  is  the  complement  of  the  latitude,  or 
is  the  co-latitude. 

The  latitude  itself  is  readily  found  by  subtracting 
this  angle  from  90°.  Thus  at  Troy  the  reading  of  the 
limb  being  found  as  above  directed  to  be  47°  16',  the 
latitude  will  be  90°— 47°  16'  =  42°  44'.  The  latitude 
may  also  be  read  direct  by  referring  to  the  inner  row  of 
figures  on  the  arc,  beginning  with  90  in  the  middle  and 
reading  to  10  on  either  side. 

TIME  FOR  USING  THE  SOLAR 

While  the  solar  attachment  can  be  used  with  advan- 
tage at  all  seasons  of  the  year,  the  most  favorable  time 
is  the  summer,  when  the  declination  is  north  and  the 
days  are  long  and  more  generally  fair.  It  is  best  not  to 
take  the  sun  at  morning  and  evening  when  it  is  within 
half  an  hour  of  the  horizon,  nor  at  noon  for  about  the 
same  interval  before  and  after  it  passes  the  meridian. 

In  favorable  weather  surveys  can  be  made  more 
rapidly  than  with  the  needle  instrument,  there  being  no 


136         W.  &  L.  E.  GURLEY/TROY,  NEW  YORK 

time  consumed  in  waiting  for  the  needle  to  settle,  or  in 
avoiding  the  errors  due  to  local  attraction. 

When  the  sun  is  obscured  the  lines  can  be  run  by 
the  needle  alone,  it  being  always  kept  with  the  sun,  or 
at  0  on  its  arc,  thus  indicating  the  direction  of  the  true 
meridian.  The  sun,  however,  must  be  regarded  as  the 
most  reliable  guide,  and  should,  if  possible,  be  taken  at 
every  station. 

GURLEY   TELESCOPIC   SOLAR   ATTACHMENT 

When  a  continued  series  of  solar  observations  are  to 
be  made,  it  is  often  desirable  that  the  main  telescope  of 
the  transit  be  used  without  disturbing  the  solar  appa- 
ratus. 

The  new  Gurley  Telescopic  Solar  Attachment  meets 
such  requirement,  as  the  main  telescope  of  the  transit 
may  be  used  independently  and  solar  observations  taken 
with  no  change  in  settings  other  than  the  hourly  change 
in  declination.  The  instrument  is  so  designed  that  its 
adjustments  can  be  accomplished  with  ease  and  pre- 
cision in  the  field. 

As  shown  in  the  illustration  on  page  138,  the 
sun  is  viewed  through  an  auxiliary  telescope,  a  reflector 
being  placed  in  front  of  the  objective  that  brings  the 
sun's  reflected  image  to  the  cross  wires. 

The  solar  telescope  is  mounted  on  a  horizontal  axis 
which  is  supported  by  a  vertical  triangular  base  fastened 
to  the  right  hand  standard.  The  solar  telescope  can 
be  moved  about  its  horizontal  axis  and  if  the  latitude  is 
laid  off  on  the  latitude  arc,  the  solar  telescope  will  coin- 
cide with  the  polar  axis. 


TRANSIT  INSTRUMENTS  137 

The  declination  arm  tilts  the  mirror  at  the  objective 
end  of  the  solar  telescope,  the  angle  being  read  on  the 
arc  attached  to  its  side.  Both  the  latitude  arc  and  the 
declination  arm  have  clamp  and  tangent  movements  for 
convenience  in  setting. 

Having  set  the  main  telescope  in  the  meridian  and 
adjusted  the  mirror  to  the  proper  declination,  the  course 
of  the  sun  is  followed  by  rotating  the  solar  telescope  in 
collar  bearings  about  its  own  axis;  an  hour  circle  sur- 
rounding the  solar  telescope  indicates  the  apparent 
time. 

The  Gurley  Telescopic  Solar  adds  but  little  weight 
and  when  furnished  in  connection  with  a  Gurley  Precise 
Mountain  Transit,  with  One  Piece  Truss  Standard,  is 
the  standard  instrument  for  public  land  surveys  and 
similar  work  requiring  exceptionally  accurate  results. 


138         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


FIG.  38 
No.  32-A  PRECISE  TRANSIT  WITH  TELESCOPIC 

SOLAR    ATTACHMENT,    U.    S.    GENERAL    LAND    OFFICE 
AND    U.     S.     FOREST    SERVICE     MODEL 


TRANSIT  INSTRUMENTS  139 

To  ADJUST  THE  GURLEY  TELESCOPIC  SOLAR 
ATTACHMENT 

TRANSIT  ADJUSTMENT.  Care  should  be  taken  to  see 
that  the  main  transit  is  adjusted  for  plate  levels,  col- 
limation  and  telescope  level  before  attempting  to  adjust 
Solar. 

FOCUSING  SOLAR.  The  eyepiece  of  the  solar  tele- 
scope is  focused  on  the  crosswires  by  rotating  the 
knurled  ring  nearest  the  eye.  The  objective  is  focused 
by  pulling  out  on  the  tube  which  holds  the  eyepiece. 

EQUATORIAL  WIRES  PARALLEL  TO  THE  Axis  OF  THE 
REFLECTOR.  Set  for  approximate  latitude  declination 
and  hour  angle,  orient  to  approximate  meridian  and 
view  the  reflected  image  of  the  sun.  Turn  the  telescope 
back  and  forth  in  hour  angle,  that  is,  in  its  collar  bear- 
ings, and  the  image  should  follow  the  wires  from  side 
to  side.  If  it  does  not,  unscrew  the  cover  ring  just 
back  of  the  knurled  head,  loosen  the  cross  wire  screws 
and  turn  the  diaphragm.  If  sun  is  not  visible  any  other 
well  defined  distant  point  may  be  used. 

COLLIMATION    OF    THE    SoLAR    TELESCOPE.       Unclamp 

the  vernier  arm  of  the  declination  arc  and  swing  the 
mirror  parallel  to  the  line  of  sight,  thus  giving  a  direct 
view  through  the  auxiliary  telescope.  Sight  on  some 
distant  point  and  revolve  the  telescope  in  its  collar  bear- 
ings 180  degrees,  adjusting  the  cross  wires  as  for  the 
Wye  Level.  The  first  adjustment  should  always  be 
checked  after  adjusting  the  collimation. 

POLAR  Axis  AT  RIGHT  ANGLES  TO  LATITUDE  Axis. 
Transit  on  fore  and  back  sights,  the  same  as  for  collima- 


140         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

ting  the  main  telescope.  If  any  adjustment  is  necessary, 
make  it  by  means  of  the  three  screws  which  are  in  the 
short  arm  on  the  upper  end  of  the  latitude  arc.  The 
middle  screw  pulls  the  eye  end  closer  to  the  transit;  the 
outside  screws  oppose  the  center  screw  and  push  the 
eye  end  farther  away. 

LATITUDE  Axis  PARALLEL  TO  TRANSIT  Axis.  Care- 
fully level  the  transit  and  make  the  solar  telescope  cut 
the  same  line  as  the  main  telescope  when  sighted  at 
some  distant  object.  Make  any  necessary  adjustment 
by  means  of  the  capstan  nuts  holding  the  lower  corner 
of  the  triangular  base  to  the  standard. 

Make  the  auxiliary  telescope  trace  the  same  vertical 
line  as  the  main  telescope,  adjusting  by  means  of  the 
capstan  nuts  at  the  upper  corner  of  the  triangular  base, 
if  necessary.  It  will  be  necessary  to  alter  the  focus  of 
the  solar  telescope  to  make  this  test.  This  test  is  similar 
to  that  for  the  adjustment  of  the  standards  of  the  main 
telescope. 

ZERO  OF  LATITUDE  ARC.  Level  the  main  telescope 
and  make  both  telescopes  agree  on  a  distant  object.  If 
the  latitude  vernier  does  not  read  zero,  loosen  the  two 
screws  at  the  back  of  the  vernier  and  correct  it.  It  is 
necessary  that  the  main  telescope  level  be  adjusted 
parallel  to  the  line  of  collimation. 

ZERO  OF  DECLINATION  ARC.  Turn  the  mirror  back 
into  position  and  set  the  declination  arm  to  read  zero. 
Through  the  auxiliary  telescope  observe  the  reflected 
image  of  some  prominent  and  distant  horizontal  object. 
Reverse  the  telescope  011  the  latitude  axis  and  view  the 


TRANSIT  INSTRUMENTS  141 

same  object.  If  the  wires  do  not  cut  the  same  point, 
make  the  adjustment  for  one  half  the  error,  by  means 
of  the  two  small  abutting  screws  in  the  middle  of  the 
declination  arm,  operating  against  the  short  arm 
attached  to  the  axis  of  the  mirror.  This  may  also  be 
checked  by  a  noon  reading  on  the  sun,  other  adjustments 
having  been  made. 

HOUR  CIRCLE.  When  the  instrument  is  pointed  in 
the  meridian,  the  hour  circle  should  read  apparent  time. 
A  screw  in  the  rim  of  the  hour  circle  on  the  side  opposite 
the  zero  hour  can  be  loosened  and  any  necessary  cor- 
rection made  by  turning  the  graduated  circle  to  the 
proper  position. 

DIRECT  OBSERVATION  ON  THE  SUN 

With  a  transit  having  both  vertical  and  horizontal 
limbs,  direct  observations  may  be  taken  on  the  sun  to 
find  the  meridian.  The  best  time  is  about  three  hours 
before  or  after  noon.  A  colored  or  smoked  glass  dark- 
ener  will  be  necessary  over  the  eyepiece  to  protect  the 
eye.  The  observations  to  be  taken  are  those  of  the  alti- 
tude of  the  sun  and  its  horizontal  angle  from  a  fixed 
point,  at  the  same  instant.  It  is  best  to  take  a  number 
of  these,  say  three  or  five,  so  as  to  check;  and  if  the 
telescope  is  reversed  and  another  set  taken,  the  mean 
of  the  two  sets  will  eliminate  many  inaccuracies.  It  is 
also  an  advantage  to  use  the  lower  limb  of  the  sun  in 
the  morning  and  the  upper  limb  in  the  afternoon,  it 
being  easier  to  judge  the  tangency  of  image  and  cross 
wires.  Allowance  is  then  made  for  the  semi-diameter 
of  the  sun,  which  varies  from  15%  to  16%  minutes. 


142         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

It  will  be  sufficiently  close  to  have  the  vertical  wire 
bisect  the  sun,  but  the  altitude  must  be  taken  with  care. 
The  transit  must  be  accurately  leveled  and  adjusted. 

To  reduce  the  observations  there  are  many  forms,  all 
deduced  from  the  same  formula.  The  form  much 
favored  is  tan'  A  =  * 


REDUCTION  FORMULA.  In  which  "A"  is  the  azimuth 
of  the  sun  or  horizontal  distance  from  the  meridian,  and 
"S"  is  one  half  the  sum  of  (90°—  altitude,  corrected 
for  refraction)  +  (90°—  latitude)  +  (90°—  declina- 
tion). Note  the  sign  of  the  declination.  When  the 
declination  is  South  this  term  would  be  90°  —  (  —  declin- 
ation) =r  90°  -f~  declination. 


TRANSIT  INSTRUMENTS  143 

EXAMPLE.     Place,   Troy,   N.   Y.        Time,   3h.   30m. 
P.  M.,  March  31,  1917. 

The  horizontal  angle  from  a  fixed  point  to  sun's 

center 241°  46' 

Observed  altitude  of  upper  limb  of  sun     ...     30°  31'  10" 
Obs.  alt. — refraction  1'  40" — semi-diameter  16'= 

alt    of   sun's    center 30°  13'  30" 

Decimation  for  day  and  hour      .    .   \    .    .     .  •    4°  02' 58" 

Latitude         42°  44' 

90°— alt.  =  59°  46'  30",  90°— dec.  =  85°  57'  02", 

90°— lat.  =  47°  16',  2  S  =  192°  59'  32"  S  =  96°  29'  46" 
log.  sin  [  S—  (90°—  alt )  ]  =  9.77664 
log.  sin  [S— (90°— lat)]  =  9.87923 


9.65587 

log.  sin  S= 9.99720 

log.  sin  [S— (90°— dec.)  ]  =  9.26251 


9.25971 

log.  tan2  y2  A  =  0.39616 
log.  tan   %  A  =  0.19808 
y2  A  =  57°  38'  06"  and  A  =  115°  16'  12"  west  of  North. 

If  in  the  morning  would  be  east  of  North. 

Apply  this  to  the  horizontal  angle  from  the  fixed 
point  to  the  sun  and  we  have  357°  02'  12",  which  is  the 
reading  of  the  horizontal  limb  when  the  telescope  is 
pointed  North.  Set  this  reading  off  on  the  limb  and 
the  telescope  will  be  in  the  plane  of  the  meridian. 


144         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


TABLE  OF  MEAN  REFRACTIONS  DUE  TO  ALTITUDE 
BAROMETER  30",  THERMOMETER  50°   F 


Apparent 
Altitude 

Mean 
Ref. 

Apparent 
Altitude 

Mean 
Ref. 

Apparent 
Altitude 

Mean 
Ref. 

Apparent 
Altitude 

Mean 
Ref. 

5° 
6° 
7° 
8° 
9° 

9'  46" 
8'  23" 
7'  20" 
6'  30" 
5'  49" 

10° 
12° 
14° 
16° 

18° 

5  16" 
4  25" 
3  47" 
3  19" 
2  56" 

20° 

25° 
30° 
35° 
40° 

2'  37" 
2'  03" 
1'  40" 
1'  22" 
1'  09" 

50° 

60° 

70° 
80° 
90° 

0'  48" 
0'  33" 
0'  21" 
0'  10" 
0'  0" 

TABLE   OF   SEMI-DIAMETERS   OF  THE   SUN 

Jan.  1, 16'  18"  April  1, 16'  02"  July  1, 15'  46"  Oct.  1, 16'  01" 
Feb.  1, 16'  16"  May  1, 15'  54"  Aug.  1, 15'  48"  Nov.  1, 16'  09" 
Mar.  1, 16'  10"  June  1, 15'  48"  Sept.  1, 15'  53"  Dec.  1. 16'  15" 


SURVEYORS  COMPASSES  145 


COMPASSES 

THE    Surveyors    Compass    is    used    considerably    for 
farm   surveys,   for   subdividing  land,   for  retracing 
old  lines,  which  were  run  originally  with   a  mag- 
netic needle,  for  exploration  and  for  other  similar  work. 

It  consists  of  a  magnetic  needle  swinging  in  a  gradu- 
ated compass  circle  mounted  on  a  plate,  to  the  ends  of 
which  two  slotted  standards  or  sight  vanes  are  attached 
in  line  with  the  zeros  of  the  graduations.  There  are 
two  levels  to  show  when  the  plates  are  horizontal,  and 
a  socket  on  which  the  instrument  can  be  turned  to  bring 
the  sights  into  line  with  the  object  sought.  The  spindle 
on  which  this  socket  turns  terminates  in  a  ball  and 
socket  joint  to  enable  the  plates  to  be  leveled. 

The  Surveyors  Compass  has  a  romantic  history  as 
it  is  associated  with  the  early  settlement  of  our  country. 
In  1748  George  Washington,  at  the  age  of  16,  took  up 
the  practice  of  surveying,  and  the  compass  of  today  is  a 
development  of  the  instrument  used  by  him  for  land 
surveys  in  Virginia.  Gurley  Compasses  were  first  used 
in  1845  and  the  accuracy  of  their  service  is  testified  by 
records  which  are  on  file  in  county  seats  throughout  the 
country. 


146         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

VERNIER  COMPASS 

THE    superiority  of  the  Vernier   Compass   over  the 
Plain  Compass  consists  in  its  adaptation  to  retrac- 
ing the  lines  of  an  old  survey  and  to  the  surveys 
of  the  United  States  public  lands,  in  which  the  lines  are 
based  on  a  true  meridian. 

MAGNETIC  NEEDLE.  A  bar  of  special  magnet  steel 
being  saturated  with  a  magnetic  charge  is  suspended  on 
a  cup  shaped  jewel  that  rests  on  the  fine  point  of  the 
center  pin  or  pivot,  about  which  it  turns  with  practically 
no  friction  so  that  it  may  assume  its  position  in  the  mag- 
netic meridian.  The  ends  are  pointed  and  swing  close 
to  the  graduated  circle  from  which  the  angular  bearing 
is  read. 

MAGNETIC  DECLINATION.  It  is  well  known  that  the 
magnetic  needle  deviates  more  or  less  to  the  east  or  west 
of  a  true  meridian,  or  north  and  south  line.  This  devia- 
tion, which  is  called  the  magnetic  declination,  is  not 
constant,  but  increases  or  decreases  to  a  very  sensible 
degree.  Thus,  at  London  the  needle  pointed  11°  east 
in  1580.  This  diminished  until  1658  when  it  was  zero, 
or  the  needle  stood  exactly  north  and  south.  The  declin- 
ation continued  westerly  until  1812,  when  the  bearing 
was  24°  west.  This  has  been  gradually  decreasing 
until  in  1916,  it  was  about  15°  west.  Thus  a  compass 
bearing  at  London  changed  from  11°  east  to  24°  west, 
or  a  total  of  35°,  from  1580  to  1812.  The  annual 
change  was  not  uniform  but  varied  from  0  to  14  minutes 
of  arc. 


SURVEYORS  COMPASSES  147 

The  time  periods  taken  for  the  needle  to  change 
from  extreme  eastern  to  extreme  western  declination 
vary  with  the  locality.  At  St.  Johns,  Newfoundland, 
the  period  was  about  180  years;  at  Trenton,  N.  J.,  130 
years  and  at  Houston,  Texas,  50  years*.  At  present  the 
annual  change  is  about  zero  in  the  middle  west,  four 
minutes  on  the  Pacific  Coast  and  six  minutes  in  New 
Hampshire. 

For  this  reason,  in  running  over  lines  from  field  notes 
of  some  years  standing,  the  surveyor  is  obliged  to  make 
an  allowance,  both  perplexing  and  uncertain,  in  the 
bearing  of  every  line.  It  was  to  obviate  this  difficulty 
that  the  Vernier  Compass  was  devised. 

To  SET  OFF  THE  DECLINATION.  It  will  be  seen  that 
the  surveyor  having  the  Vernier  Compass  can,  by  mov- 
ing the  vernier  to  either  side,  and  with  it,  of  course,  the 
compass  circle  attached,  set  the  compass  to  any  declin- 
ation. 

He  therefore  places  his  instrument  on  some  well 
defined  line  of  the  old  survey,  and  turns  the  pinion  until 
the  needle  of  his  compass  indicates  the  same  bearing  as 
that  given  in  the  field  notes  of  the  original  survey. 
Then,  clamping  the  vernier,  he  can  run  all  the  other 
lines  from  the  old  field  notes  without  further  alteration. 


*From  a  speech  at  the  Centennial  Celebration  of  the 
N.  S.  C.  fy  G.  S.,  made  by  Doctor  Louis  A.  Bauer,  Direc- 
tor of  the  Department  of  Terrestrial  Magnetism  of  the 
Carnegie  Institute,  at  Washington,  D.  C. 


148         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  reading  of  the  vernier  on  the  limb  in  such  a  case 
would  show  the  change  of  declination  of  the  two  diff- 
erent periods. 

The  magnetic  declination  at  any  place  being  known, 
a  true  meridian,  or  north  and  south  line,  may  be  run  by 
moving  the  vernier  to  either  side,  as  the  declination  is 
east  or  west,  until  the  arc  passed  over  on  the  limb  is 
equal  to  the  angle  of  declination,  and  then  turning  the 
compass  until  the  needle  is  made  to  cut  the  zeros  on  the 
graduated  circle.  The  line  of  sights  will  then  give  the 
direction  of  the  true  meridian  of  the  place. 

Such  a  change  in  the  position  of  the  vernier  is  nec- 
essary in  surveying  the  United  States  public  lands, 
which  surveys  are  always  run  from  the  true  meridian. 

THE  LINE  OF  No  DECLINATION,  or  the  line  upon 
which  the  needle  will  indicate  a  true  north  and  south 
direction,  is  situated  in  the  United  States  nearly  in  an 
imaginary  line  drawn  from  the  middle  of  Lake  Superior 
to  Savannah,  Ga. 

A  magnetic  needle  placed  east  of  this  line  has  a 
declination  to  the  west,  and  when  placed  west  of  the 
line  the  declination  is  to  the  east;  and  in  both  cases  it 
increases  as  the  needle  is  carried  farther  from  the  line 
of  no  declination. 

Thus,  in  Minnesota,  the  declination  is  from  eight  to 
eleven  degrees  to  the  east,  while  in  Maine  it  is  from 
fifteen  to  nineteen  degrees  to  the  west.  At  Troy,  in 
the  year  1919,  the  declination  was  about  12°  33'  to  the 
west,  and  is  increasing  now  in  the  same  direction  about 
5.6  minutes  annually. 


SURVEYORS  COMPASSES  149 

DIURNAL  VARIATION.  The  magnetic  declination  does 
not  remain  constant  through  an  entire  day,  but  reaches 
its  farthest  point  east  about  8  o'clock  A.  M.,  and  its 
farthest  point  west  about  2  o'clock  P.  M. 

Conditions  of  temperature,  magnetic  storms  and 
other  causes  at  times  affect  the  needle.  Our  own  exper- 
iments show  that  different  needles  observed  at  the  same 
time  and  under  the  same  conditions  differ  in  their  direc- 
tion, but  show  nearly  the  same  daily  change. 

NEEDLE  LIFTER.  Underneath  the  main  plate  is  a 
needle  lifting  screw  which,  by  moving  a  concealed  spring, 
raises  the  needle  from  the  pivot,  and  thus  prevents 
injury  to  the  jewelled  center  as  well  as  the  blunting  of 
the  point  during  transportation  or  while  carrying  the 
instrument  in  the  field. 

When  the  compass  is  not  in  use,  it  is  the  practice  of 
many  surveyors  to  let  down  the  needle  upon  the  point 
of  the  center  pin,  and  allow  it  to  assume  its  position  in 
the  magnetic  meridian,  so  as  to  retain  its  polarity. 
After  the  needle  has  settled  it  should  be  raised  against 
the  glass  for  the  reasons  stated  above. 

PLATE  LEVELS.  The  spirit  levels  are  placed  at  right 
angles  with  each  other  so  as  to  level  the  plate  in  all 
directions,  and  are  balanced  upon  a  pivot  under  the 
middle  of  the  tube,  so  as  to  be  adjustable  by  a  screw 
driver. 

OUTKEEPER.  A  small  dial  plate,  having  an  index, 
turned  by  a  milled  head  underneath,  is  used  with  this 
compass  to  keep  tally  in  chaining.  The  dial  is  figured 
from  0  to  16,  the  index  being  moved  one  notch  for  every 
chain  run. 


150         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

BRASS  COVER.  A  brass  cover  is  fitted  over  the  glass 
of  the  compass,  and  serves  to  protect  it  from  accident, 
as  well  as  to  prevent  electric  disturbance. 

SIGHTS.  The  sights,  or  sight  vanes,  have  fine  slits 
cut  through  nearly  their  whole  length,  terminated  at 
intervals  by  circular  apertures,  through  which  the  object 


FIG.  39 
No.  226  VERNIER  COMPASS 

sighted  upon  is  more  readily  found.  Sometimes  a  horse 
hair  or  wire  is  substituted  for  half  the  slit,  and  placed 
alternately  with  it  on  opposite  sights. 


SURVEYORS  COMPASSES  151 

The  telescopic  sight  is  often  used  with  the  Vernier 
Compass,  and  its  adjustments  and  use  are  described  on 
pages  158  to  165, 

TANGENT  SCALE.  The  edges  of  the  north  sight  of 
our  compasses  are  graduated  to  half  degrees  for  angles 
of  elevation  and  depression  respectively,  which  are  read 
from  corresponding  peep  sights  on  the  south  vane. 

The  maximum  angle  which  can  be  read  is  23  degrees. 

BALL  SPINDLE.  The  compass  is  fitted  to  a  spindle 
made  slightly  conical,  and  having  on  its  lower  end  a  ball 
turned  perfectly  spherical,  and  confined  in  a  socket  by 
a  pressure  so  light  that  the  ball  can  be  moved  in  any 
direction  in  leveling  the  compass.  The  ball  is  placed 
either  in  the  brass  head  of  the  staff,  or  better,  in  the 
compass  tripod. 

A  leveling  adopter,  shown  on  page  158,  is  often  used 
for  more  convenient  leveling  of  the  compass. 

THE  STAFF  MOUNTINGS  consist  of  the  brass  head 
already  mentioned,  and  a  pointed  steel  shoe.  The  staff, 
to  which  the  mountings  should  be  securely  fastened,  may 
be  procured  from  any  wheelwright,  or  provided  by  the 
surveyor  himself. 

CLAMP  SCREW.  In  the  side  of  the  hollow  socket  of 
the  compass  is  a  screw  by  which  the  instrument  may  be 
clamped  to  the  spindle  in  any  position. 

SPRING  CATCH.  Besides  the  clamp  screw  there  is 
fitted  to  the  socket  of  our  Vernier  Compass  No.  226,  a 
spring  catch,  which,  as  soon  as  the  instrument  is  set  upon 
its  spindle,  slips  into  a  groove,  and  thus  removes  all 


152         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

danger  of  the  instrument  falling  from  the  spindle  while 
being  carried. 

USE  OF  THE  COMPASS 

In  using  the  compass,  the  surveyor  should  keep  the 
south  end  toward  his  person,  and  read  the  bearings  from 
the  north  end  of  the  needle.  The  E  and  W  letters  on 
the  face  of  the  compass  are  transposed  because  the 
needle  represents  a  fixed  line,  about  which  the  compass 
box  is  revolved  in  directing  the  sight  to  the  object 
observed.  In  sighting  a  point  situated  NW,  the  needle 
will  point  E  of  the  line  of  sight,  but  it  will  correctly 
read  NW  in  accordance  with  the  line  actually  sighted, 
because  the  East  quadrant  is  marked  West. 

The  compass  circle  being  graduated  to  half  degrees, 
a  little  practice  will  enable  the  surveyor  to  read  the 
bearings  to  quarter  degrees  or  even  less,  estimating  with 
his  eye  the  space  bisected  by  the  point  of  the  needle; 
and  as  this  is  as  close  as  the  traverse  table  is  usually 
calculated,  it  is  the  general  practice. 

ANGLES  OF  ELEVATION.  Having  leveled  the  com- 
pass, bring  the  south  end  toward  the  person,  place  the 
eye  at  the  little  button,  or  peep  sight,  on  the  right  side  of 
the  south  sight,  and  with  the  hand  hold  a  card  on  the 
front  surface  of  the  north  sight,  so  that  its  top  edge 
will  be  at  right  angles  with  the  graduated  edge  and 
coincide  with  the  zero  mark.  Then,  sighting  over  the 
top  of  the  card,  note  upon  a  flagstaff,  held  near  the  com- 
pass, the  height  cut  by  the  line  of  sight,  move  the  staff 
up  the  elevation  and  carry  the  card  along  the  sight  until 


SURVEYORS  COMPASSES  153 

the  line  of  sight  again  cuts  the  same  height  on  the  staff. 
Read  off  the  degrees  and  half  degrees  passed  over  by 
the  card,  and  this  will  be  the  angle  required. 

ANGLES  OF  DEPRESSION.  Proceed  in  the  same  man- 
ner, using  the  eyepiece  and  graduations  on  the  opposite 
side  of  the  sight,  and  reading  from  the  top  of  the  sight. 

NEW  AND  OLD  SURVEYS.  When  the  compass  is  to  be 
used  in  making  new  surveys,  the  vernier  should  be  set 
at  zero  and  clamped  by  the  nut  on  the  plate. 

In  surveying  old  lines,  the  change  of  the  magnetic 
declination  should  be  ascertained  by  setting  the  compass 
on  some  well  defined  line  of  the  tract,  and  making  the 
bearing  agree  with  that  of  the  old  survey,  by  moving 
the  circle  as  already  described.  The  circle  can  then  be 
clamped,  and  the  old  lines  retraced  from  the  bearings 
given  by  the  original  surveyor. 

ELECTRICITY.  Caution  should  be  exercised  in  hand- 
ling the  compass,  that  the  glass  face  does  not  become 
charged  with  electricity  excited  by  the  friction  of  cloth, 
silk,  or  the  hand,  so  as  to  attract  the  needle  to  its  under 
surface.  Should  the  glass  become  so  charged,  however, 
the  electricity  may  be  removed  by  breathing  upon  it,  or 
by  touching  different  parts  of  its  surface  with  the 
moistened  finger.  Ignorance  of  this  apparently  trifling 
matter  has  caused  the  inexperienced  surveyor  much 
annoyance. 


154,         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


COMPASS  ADJUSTMENTS 

To  ADJUST  THE  PLATE  LEVELS.  Bring  the  level 
bubbles  into  the  middle  by  the  pressure  of  the  hand  on 
different  parts  of  the  plate,  and  turn  the  compass  half 
way  around.  If  the  bubbles  run  to  the  end  of  the  tubes, 
it  indicates  that  those  ends  are  the  highest.  Lower  them 
by  loosening  the  screws  under  the  lowest  ends  and 
tightening  those  under  the  highest  ends  until,  by  estima- 
tion, the  error  is  half  removed.  Level  the  plate  again, 
and  repeat  the  first  operation  until  the  bubbles  will 
remain  in  the  middle  during  an  entire  revolution  of  the 
compass. 

To  ADJUST  THE  SIGHTS.  The  sights  may  next  be 
tested  by  observing  through  the  slits  a  hair  or  thread, 
made  exactly  vertical  by  a  plummet.  Should  the  hair 
appear  on  the  side  of  the  slit,  the  sight  must  be  adjusted 
by  filing  its  under  surface  on  the  side  which  seems  the 
highest. 

To  ADJUST  THE  NEEDLE.  Having  the  eye  nearly  in 
the  same  plane  with  the  graduated  rim  of  the  compass 
circle,  with  a  splinter  of  wood  or  an  iron  wire  bring  one 
end  of  the  needle  in  line  with  any  prominent  graduation 
of  the  circle,  as  the  zero  or  the  ninety  degree  mark,  and 
notice  if  the  other  end  corresponds  with  the  degree  on 
the  opposite  side.  If  it  does  not,  use  the  small  brass 
wrench  furnished  with  our  compasses,  and  bend  the 
center  pin  about  one  eighth  of  an  inch  below  the  point, 
until  the  ends  of  the  needle  are  brought  into  line  with 
the  opposite  degrees. 


SURVEYORS  COMPASSES  155 

Then,  holding  the  needle  in  the  same  position,  turn 
the  compass  half  way  around,  and  note  whether  it  now 
cuts  opposite  degrees.  If  not,  correct  half  the  error  by 
bending  the  needle,  and  the  remainder  by  bending  the 
center  pin.  The  operation  should  be  repeated  until 
perfect  reversion  is  secured  in  the  first  position. 

This  being  obtained,  it  may  be  tried  on  another  quar- 
ter of  the  circle.  If  any  error  is  there  manifested,  the 
correction  must  be  made  in  the  center  pin  only,  the 
needle  having  been  already  straightened  by  the  previous 
operation. 

When  again  made  to  cut,  it  should  be  tried  on  the 
other  quarters  of  the  circle,  and  corrections  made  in  the 
same  manner  until  the  error  is  entirely  removed,  and 
the  needle  will  reverse  in  every  point  of  the  graduated 
surface. 

REPAIRS   TO   THE    COMPASS 

To  enable  the  surveyor  to  make  such  repairs  as  are 
possible  without  recourse  to  an  instrument  maker,  we 
add  a  few  simple  directions. 

NEEDLE.  The  magnetic  needle  is  the  most  vexatious 
and  troublesome  part  of  a  surveyor's  instrument,  and  its 
imperfect  working  is  almost  invariably  due  to  a  rough- 
ened or  scratched  jewel  or  to  a  dulled  center  pin,  or  to 
both,  and  rarely  to  loss  of  magnetism. 

Injuries  to  the  jewel  and  center  pin  are  generally 
caused  by  allowing  the  needle  to  swing  on  the  pin  when 
the  instrument  is  transported  or  when  it  is  carried  in 


156         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

the  field  from  one  station  to  another.  If  the  needle  is 
sufficiently  raised  by  means  of  the  needle  lifting  screw 
so  that  there  is-  no  contact  between  the  jewel  and  the 
center  pin,  the  most  frequent  cause  of  injuries  will  be 
avoided. 

A  wire  is  coiled  on  the  south  end  of  the  needle,  and 
may  be  moved  back  and  forth  to  counterbalance  the  vary- 
ing magnetic  dip  at  the  north  end,  as  a  needle  which  is 
perfectly  balanced  in  one  locality  is  frequently  out  of 
balance  in  a  different  latitude. 

It  may  sometimes  happen  that  the  needle  has  lost 
its  polarity  and  must  be  remagnetized.  To  do  this, 
proceed  as  follows:  Unscrew  the  bezel  ring  that  holds 
the  glass  face,  and  remove  the  needle.  Pass  each  end 
of  the  needle  from  middle  to  extremity  with  a  gentle 
pressure  over  the  magnetic  pole  of  a  permanent  magnet, 
describing  before  each  pass  a  circle  of  about  six  inches 
radius,  to  which  the  surface  of  the  pole  is  tangent,  draw- 
ing the  needle  toward  the  body,  and  taking  care  that  the 
north  and  the  south  ends  are  applied  to  the  opposite 
poles  of  the  magnet. 

Should  the  needle  be  returned  in  a  path  near  the 
magnetic  pole,  the  magnetism  induced  by  the  contact  of 
the  needle  with  the  magnet,  in  the  pass  just  described, 
would  be  reversed,  and  the  magnetic  virtue  almost  entire- 
ly neutralized  at  each  operation.  When  the  needle  has 
been  passed  in  this  manner  about  twenty-five  times  in 
succession,  it  will  be  fully  magnetized. 

CENTER  PIN.  The  center  pin  should  occasionally 
be  examined,  and,  if  much  dulled,  should  be  taken  out 


SURVEYORS  COMPASSES  157 

with  the  brass  wrench  or  with  a  pair  of  pliers,  and 
sharpened  on  a  hard  oilstone,  the  operator  placing  it  in 
the  end  of  a  small  stem  of  wood,  or  in  a  pin  vise,  and 
delicately  twirling  it  with  the  fingers  as  he  moves  it 
back  and  forth  at  an  angle  of  about  thirty  degrees  with 
the  surface  of  the  stone. 

When  the  point  is  made  so  fine  and  sharp  as  to  be 
invisible  to  the  eye,  it  should  be  smoothed  by  rubbing 
it  on  the  surface  of  a  soft  and  clean  piece  of  leather. 

To  REPLACE  A  LEVEL  VIAL.  See  instructions  under 
transits,  page  66. 

ATTACHMENTS  FOR  VERNIER  COMPASS 

LEVELING  ADOPTER.  For  more  convenient  leveling 
of  the  compass,  as  well  as  other  instruments,  we  make 
a  Leveling  Adopter,  No.  241,  which  is  screwed  to  the 
top  of  the  tripod  like  the  leveling  head.  It  can  be  used 
with  a  simple  ball  spindle  and  can  be  supplied  with 
Compass  No.  226. 

The  instrument  is  made  approximately  level  upon 
the  ball  and  finally  made  truly  horizontal  by  the  level- 
ing screws. 

LEVELING  HEAD.  We  also  make  for  use  with  Com- 
pass No.  226  a  Leveling  Head,  No.  242,  consisting  of 
arms  strongly  ribbed  with  four  leveling  screws  having 
dust  caps,  and  with  clamp  and  tangent  movement. 

This  Leveling  Head  furnishes  a  stable  support  for 
the  instrument,  and  affords  the  same  conveniences  for 
leveling  and  accurate  adjustment  in  azimuth  as  the 
leveling  heads  on  transits  or  levels. 


158         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


TELESCOPIC  SIGHT.  This  telescope  is  attached  to  a 
movable  band  which,  as  shown  in  the  illustration,  can 
be  slipped  over  the  sight  of  a  compass,  clamped  at  any 
point  desired,  and  adjusted  with  a  screw  driver  and  a 
steel  adjusting  pin. 


No.  241 


FIG.  40 
No'.  241  LEVELING  ADOPTER 

To  put  this  attachment  in  place,  slip  the  band  over 
the  south  sight  of  the  compass,  having  the  telescope  at 
the  right  hand  and  the  clamp  screw  on  the  outer  surface 
of  the  sight,  placing  the  band  as  low  as  will  allow  the 


SURVEYORS  COMPASSES 


159 


telescope  to  revolve  without  striking  the  compass.  This 
place  should  be  marked  by  a  line  across  the  sight,  or  by 
a  screw  or  pin  on  the  inner  surface  of  the  sight,  that  the 
band  may  be  set  at  the  same  point  in  subsequent  use. 


FIG.  41 
No.  242  LEVELING  HEAD 

To  fasten  the  band  to  the  sight,  bring  up  the  clamp 
screw  with  a  pressure  just  sufficient  to  hold  the  band  to 
its  place,  tighten  the  screw  on  the  left  until  the  band  is 


160         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

against  the  right  edge  of  the  sight,  and  finally  tighten 
the  clamp  screw. 

To  focus  the  telescope,  turn  the  end  of  the  eyepiece 
by  the  spiral  motion  of  the  tube  until  the  cross  wires 
are  brought  into  distinct  view.  The  objective  is  then 


FIG.  42 

NO.  262  TELESCOPIC  SIGHT,  WITH  ATTACHED  VERTICAL 

CIRCLE  NO.  265,  LEVEL  ON  TELESCOPE  NO.  266, 

AND  CLAMP  AND  TANGENT  NO.  267 

moved  in  either  direction  by  the  pinion  on  the  side  of 
the  telescope,  until  the  object  is  clearly  seen. 


SURVEYORS  COMPASSES  161 

The  optical  axis  of  the  Telescopic  Sight  is  at  one 
side  of  the  line  of  sight  of  the  sight  vanes,  but  parallel 
with  it.  The  difference  between  a  sight  taken  with  the 
sight  vanes  and  one  taken  with  the  telescope  is  so  small 
that  it  may  be  disregarded  in  any  survey  made  with  the 
magnetic  needle.  If  all  the  lines  are  run  with  the  Tele- 
scopic Sight,  the  angles  measured  will  be  as  accurate  as 
if  the  optical  axis  of  the  telescope  was  in  the  line  of 
sight  of  the  sight  vanes. 

The  telescope  is  nine  inches  long,  has  a  power  of 
about  20  diameters  and  is  furnished  with  stadia  wires 
in  addition  to  the  cross  wires. 

OFFSET  STANDARD.  When  desired,  the  Telescopic 
Sight  may  be  mounted  upon  an  Offset  Standard  with 
Counterpoise,  and  so  arranged  that  the  line  of  sight  is 
in  line  with  the  zeros  of  the  compass  circle.  When  in 
use,  this  standard  with  the  telescope  attached,  is  substi- 
tuted for  the  south  sight  of  the  compass. 

When  furnished  with  a  new  instrument  the  telescope 
is  packed  in  the  box  with  the  compass,  but  it  can  be 
safely  sent  by  mail  to  any  part  of  the  country,  packed 
in  a  case  in  which  it  may  be  kept  when  not  in  use. 

In  the  illustration  on  page  160,  the  telescope  No.  262 
is  shown  fitted  with  a  vertical  circle,  a  level,  and  clamp 
and  tangent.  For  simple  sighting,  the  level  and  circle 
can,  of  course,  be  dispensed  with,  but  in  the  use  of  the 
stadia  they  are  very  desirable. 

When  measurements  are  to  be  recorded  in  chains 
and  links,  the  stadia  wires  should  be  made  to  cover  one 


162         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

foot  at  a  distance  of  sixty-six  feet;  if  recorded  in  feet, 
the  wires  should  cover  one  foot  at  a  distance  of  one 
hundred  feet. 

The  rod  used  with  the  stadia  should  be  graduated  to 
feet  and  decimals  of  a  foot.  The  various  styles  of  rods 
are  more  fully  described  on  pages  206  to  237. 


FIG.  43 

COMPASS  FITTED  WITH  NO.  262  TELESCOPIC  SIGHT  HAVING 

LEVEL,  CLAMP  AND  TANGENT  AND  VERTICAL 

CIRCLE,  MOUNTED  ON  NO.  268  OFFSET 

STANDARD  WITH  COUNTERPOISE 


SURVEYORS  COMPASSES  163 

In  using  the  stadia,  the  lower  wire  is  brought  by  the 
tangent  screw  precisely  upon  an  even  foot  graduation 
of  the  rod,  the  upper  wire  is  read,  the  smaller  reading 
subtracted  from  the  larger  and  the  distance  recorded. 

ADVANTAGE  OF  THE  TELESCOPE.  The  advantage  of 
the  telescope  over  the  sight  vanes  is  readily  apparent. 
Much  longer  sights  can  be  taken,  either  fore  or  back, 
and  lines  run  up  and  down  steep  hillsides  with  the  same 
facility  as  on  level  ground,  and  with  mor?  accuracy,  and 
with  great  relief  to  the  eyes  of  the  surveyor,  often  se- 
verely strained  by  the  use  of  the  sight  vanes  of  the 
compass.  Indeed,  it  may  be  said  that  with  this  simple 
attachment  every  compass  can  be  transformed  into  a 
transit  compass,  and  the  advantages  of  the  telescope 
brought  within  the  reach  of  every  surveyor,  at  small 
cost. 

To  ADJUST  THE   TELESCOPIC   SIGHT 

To  make  the  adjustments,  and  indeed  to  do  any 
correct  work  with  a  compass,  the  level  bubbles  should 
remain  in  the  middle  when  the  instrument  is  turned 
upon  its  spindle,  and  the  sights  should  trace  a  vertical 
line  when  the  compass  is  level. 

The  means  of  effecting  the  adjustments  will  be 
understood  by  referring  to  page  164. 

TELESCOPE  Axis.  To  make  the  telescope  axis  hori- 
zontal, the  compass  being  in  good  order,  first  bring  the 
levels  into  the  middle  and  place  the  band  in  position 
upon  the  sight,  as  before  described.  Focus  the  tele- 


164         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


scope,  and  set  the  vertical  cross  wire  on  the  edge  of  a 
building,  or  a  long  plumb  line,  50  to  60  feet  distant. 
If  the  vertical  wire  is  not  parallel  with  the  edge  or  line, 
loosen  the  capstan  head  screws  and  turn  the  diaphragm 
by  the  screw  heads  until  the  correction  is  made,  then 
tighten  the  screws.  Next,  sight  at  a  point  on  the  edge 
or  line,  near  the  ground. 

Clamp  the  compass  to  the  spindle,  and  point  the 
telescope  to  the  top  of  the  building  or  line.  If  the  wire 
strikes  to  the  right  of  the  edge,  it  shows  that  the  right 
end  of  the  telescope  axis  is  the  lowest. 

To  raise  it,  loosen  the  screws,  B  B,  C  C,  which  hold 
the  piece  containing  the  axis  of  the  telescope,  and  by  the 
screws,    D    D,    the    lower    of 
which  should  be  unscrewed  and 
the  upper  one  tightened,  raise 
the  telescope  until  the  wire  will 
follow   the   vertical   line. 

If  the  cross  wire  strikes  to 
the  left  when  the  telescope  is 
raised,  proceed  exactly  the  re- 
verse in  making  the  correction, 
until  the  wire  will  follow  the 
edge  from  one.  end  to  the  other. 

LINE  OF  COLLIMATION.  To  bring  the  line  of  collima- 
tion  into  a  position  at  right  angles  with  the  axis  of  the 
telescope,  so  that  the  cross  wires  will  indicate  two  points 
in  opposite  directions  in  the  same  straight  line,  proceed 
as  directed  for  transits  on  pages  77  to  79. 


SURVEYORS  COMPASSES  165 

ADJUSTMENT  OF  TELESCOPE  TO  THE  SIGHTS.  Find 
an  object  from  three  hundred  to  four  hundred  feet  dis- 
tant, which  the  sight  vanes  will  intersect.  Clamp  to  the 
spindle  and  sight  through  the  telescope  at  the  object. 
If  the  vertical  wire  strikes  to  the  right,  loosen  the  screws 
B  B,  and  screw  up  those  in  front,  marked  F  F,  the  ends 
only  of  which  are  shown  in  the  figure,  until  the  vertical 
wire  bisects  the  object,  looking  again  through  the  vanes 
to  see  that  the  same  object  is  seen  through  both  telescope 
and  sights.  If  the  cross  wire  should  strike  to  the  left 
of  the  object,  proceed  in  a  manner  exactly  the  reverse 
until  the  error  is  corrected. 


166         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

COMPASS  WITH  LIMB  AND  TELESCOPE 
1920  MODEL 

This  new  model  was  designed  to  meet  the  needs  of 
engineers  and  surveyors  who  do  not  have  constant  use 
for  an  expensive  transit  and  yet  desire  an  instrument 
which  will  enable  them  to  do  a  greater  variety  of  work 
than  is  possible  with  the  ordinary  sight  compass. 

It  is  a  highly  developed  form  of  a  Telescope  Compass 
and  has  the  added  characteristics  of  a  light  Transit; 
thus  it  can  be  successfully  used  for  ordinary  land  sur- 
veying, preliminary  or  reconnoissance  surveys,  mine 
surveys,  etc.,  in  fact  for  a  variety  of  work  in  which 
rapidity,  ease  of  operation  and  portability,  rather  than 
extreme  accuracy,  are  the  essential  factors.  Engineers 
and  Surveyors,  as  well  as  Explorers,  will  find  this 
instrument  a  desirable  addition  to  their  equipment, 
enabling  them  to  reserve  their  valuable  Transits  for  pre- 
cise work.  The  needle  is  of  unusual  length  for  such  a 
compact  instrumnt,  making  it  ideal  for  accurate  com- 
pass surveys. 

The  weight  of  the  compass  without  the  tripod  is 
seven  and  one  quarter  pounds  and  the  tripod  weighs 
about  four  and  one  half  pounds. 


SURVEYORS  COMPASSES 


167 


FIG.  44 
No.  294  COMPASS  WITH  LIMB  AND  TELESCOPE 

SUPERSEDING  INSTRUMENTS  PREVIOUSLY  LISTED  AS  NO.  293 
AND    NO.    293-A 


168         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

POCKET  COMPASSES 

WE    manufacture    a    variety    of    small    instruments 
which  are  so  portable  and  at  the  same  time  so 
efficient  that  they  are  often  used,  in  preference 
to  the  larger  ones,  for  preliminary    or    reconnoissance 
work. 


FIG.  45 
No.  285  POCKET  COMPASS  WITH  LIMB 


SURVEYORS  COMPASSES  169 


POCKET  COMPASS  WITH  LIMB 

The  limb  of  this  compass  is  five  inches  in  diameter, 
graduated  to  half  degrees  and  figured  like  limb  I  page 
36.  The  vernier  which  is  placed  at  an  angle  of  30 
minutes  to  the  line  of  sight  reads  to  single  minutes. 

The  needle  circle  is  graduated  to  half  degrees  and 
is  figured  from  0  to  90  each  way.  The  needle  is  three 
and  one  half  inches  long  and  the  magnetic  declination 
can  be  set  off  to  single  minutes. 

The  sights  fold  down  closely  for  convenience  in 
packing  and  are  made  half  slit  and  half  hair  so  that 
back  sights  may  be  taken  without  turning  the  limb. 

This  instrument  can  be  used  for  a  great  variety  of 
work  and  with  the  light  extension  tripod  is  especially 
adapted  to  surveys  of  mines  where  angles  must  be  taken 
independently  of  the  needle. 


170         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

GEOLOGISTS  COMPASS 

This  compass  has  proven  admirably  adapted  for 
topographical  work,  and  has  been  adopted  by  the  U.  S. 
Forest  Service  for  the  use  of  field  men  in  making  forest 
surveys  and  maps.  If  properly  used,  accurate  work 
can  be  done  with  this  small  and  compact  instrument. 

It  is  made  of  aluminum  to  decrease  weight  and  has  a 
needle  2%  inches  long  enclosed  with  its  compass  circle 
in  a  circular  box  set  on  a  plate  4  inches  square.  With 
the  improved  needle  lifter  as  shown,  a  water  and  dust- 
proof  needle  box  is  assured. 

The  edges  of  this  base  are  beveled  and  graduated, 
two  for  a  tangent  scale  and  two  to  inch  scales.  One  of 
these  latter  is  graduated  to  eighths,  each  of  which  repre- 
sents ten  chains,  and  the  other  is  decimal.  The  compass 
circle  is  made  movable,  and  by  a  vernier  attached  to  it 
on  the  inside  the  magnetic  declination  may  be  set  off 
to  5  minutes. 

On  the  under  side  of  the  plate  is  a  township  plat. 

On  the  compass  face  is  an  arc  of  180  degrees  figured 
on  each  side  of  the  0  line  from  0  to  90.  A  weighted 
pendulum  hung  from  the  center  pin  indicates,  by  its 
pointer  on  this  arc,  the  angle  of  slope,  when  the  com- 
pass is  placed  so  that  it  rests  on  its  west  edge.  On  the 
outside  of  the  box  containing  the  compass  circle  is  a 
movable  circle,  beveled  and  graduated  on  its  upper  edge 
and  figured  from  0  to  90,  and  having  at  each  quadrant 
a  slit  for  sighting. 


SURVEYORS  COMPASSES 


171 


FIG.  46 
No.   335  GEOLOGISTS  COMPASS 

U.   S.    FOREST   SERVICE   PATTERN 


172         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Two  tall  folding  sights  are  attached  to  the  edge  of 
the  circular  box,  one  having  a  slit  and  the  other  a  hair. 
Two  levels  are  placed  at  right  angles  with  each  other 
upon  the  base. 

The  compass  is  supported  on  a  simple  ball  spindle 
and  socket,  with  staff  mountings,  and  is  usually  carried 
in  a  leather  pouch  with  shoulder  and  belt  straps.  Such 
a  pouch  can  be  supplied  for  an  extra  price. 

The  staff  cap  is  slotted  to  allow  vertical  angles  to 
be  read  by  means  of  the  pendulum  while  the  compass  is 
on  the  staff  or  tripod. 

Tripods  Nos.  416,  421  and  426  are  suitable  for  use 
with  this  compass. 


SURVEYORS  COMPASSES  173 

THE  Dip  Compass  consists  essentially  of  a  magnetic 
needle  so  suspended  as  to  move  readily  in  a  vertical 
direction,  the  angle  of  inclination,  or  "dip,"  being 
measured  upon  the  graduated  rim  of  the  compass  circle. 

When  in  use,  the  ring  or  ball  is  held  by  the  hand, 
and  the  compass  box  by  its  own  weight  assumes  a  verti- 
cal position.  It  must  be  held  in  the  plane  of  the  magnetic 
meridian.  In  this  position  the  needle,  when  unaffected 
by  the  attraction  of  iron,  assumes  a  horizontal  line,  as 
shown  by  the  zeros  of  the  circle.  When  brought  over 
any  mass  of  magnetic  iron  ore  it  dips,  and  thus  detects 
the  presence  of  such  ore  with  certainty. 

If  the  Dip  Compass  is  held  horizontal,  it  serves  as 
an  ordinary  pocket  compass,  and  indicates  the  magnetic 
meridian,  in  the  plane  of  which  it  should  be  held  when 
used  to  ascertain  the  dip. 

Dip  Compasses  have  a  3  inch  needle,  provided  with 
a  stop  which  is  released  by  screwing  down  the  clamp  in 
the  ball.  The  new  style  needle  clamp  enables  the 
instrument  to  be  held  and  controlled  to  the  best  advan- 
tage. The  improved  form  of  needle  release  is  positive 
in  action,  durable  in  construction  and  not  liable  to  in- 
jury. The  Compasses  have  the  two  sides  of  glass  and 
are  furnished  with  removable  brass  covers. 

The  needle  of  our  Dip  Compasses  is  adjusted  to  read 
0  at  Troy,  N.  Y.,  when  held  in  the  plane  of  the  mag- 
netic meridian,  but  it  may  read  differently  in  another 
place. 


174         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  readings  of  these  compass  needles  are  always 
relative  and  not  absolute;  therefore,  if  a  needle  is  held 
in  the  plane  of  the  meridian,  in  a  place  where  it  is 
known  that  there  is  no  magnetic  attraction,  and  the 


FIG.  47 
No.  341-A  DIP  COMPASS 

reading  is  carefully  noted;  and  the  needle  is  then  held 
in  the  plane  of  the  meridian  where  magnetic  attraction 


SURVEYORS  COMPASSES  175 

is  suspected,  a  different  reading  will  show  the  presence 
of  some  magnetic  body,  whether  the  needle  is,  in  the 
first  case,  perfectly  horizontal  (reads  to  zero)  or  not. 

When  in  use  the  needle  should  always  be  held  so 
that  it  will  swing  freely  in  the  plane  of  the  meridian, 
the  stops  being  drawn  entirely  out  of  the  way. 

When  not  in  use  the  clamp  should  be  unscrewed  so 
that  the  needle  is  securely  held. 

There  is  no  instrument  made  which  will  indicate  the 
presence  of  gold  or  silver. 


176         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


FIG.  48 
No.  350  DIAL  COMPASS 

U.  S.  GEOLOGICAL  SURVEY  PATTERN 


SURVEYORS  COMPASSES  177 

DIAL  COMPASS 

A  rough  method  of  detecting  the  presence  of  large 
bodies  of  magnetic  ore  is  by  a  compass  directed  in  the 
meridian  by  means  of  apparent  time  on  a  Sun  dial. 
Allowing  for  the  magnetic  declination  for  that  location 
any  variation  by  the  needle  from  the  magnetic  meridian 
will  indicate  local  attraction.  This  instrument,  made 
of  aluminum,  has  a  needle  two  and  five  eighths  inches 
long,  and  with  its  compass  circle  is  enclosed  in  a  circular 
box  set  upon  a  base  4  inches  square,  three  edges  of 
which  are  chamfered  and  graduated,  the  one  on  the  W 
side  of  the  compass  into  inches  and  tenths  and  the  two 
others  into  degrees  and  half  degrees,  and  figured  from 
a  center  on  the  southwest  corner  of  the  base. 

The  compass  circle  is  movable,  in  order  to  set  off  the 
magnetic  declination,  and  has  a  vernier  attached  to  it 
on  the  inside,  by  which  a  graduated  arc  on  the  face  of 
the  compass  is  read  to  5  minutes. 

With  the  improved  needle  lifter  as  shown,  a  water 
and  dust-proof  compass  box  is  assured.  The  staff  cap 
is  slotted  to  allow  vertical  angles  to  be  read  by  means 
of  the  pendulum  while  the  compass  is  on  the  staff  or 
tripod. 

There  is  also  on  the  south  side  of  the  face  an  arc 
of  180  degrees,  figured  from  0  to  90  on  each  side  of  the 
south  or  zero  line  of  the  face. 

A  pendulum  with  index  point  hung  from  the  center 
pin  reads  this  arc  when  the  compass  is  set  up  vertical 
on  the  raised  south  edge,  thus  making  it  a  clinometer  or 
slope  measurer. 


180         W.  &  L.  E.  GURLEY,  TROY,  N^w  YORK 


FIG.  49 
No.  3154  WOOD  Box  POCKET  COMPASS 


SURVEYORS   COMPASSES 


180-A 


POCKET  VERNIER  COMPASS 


Nos.  300  AND  305 


The  Pocket  Vernier  Compass  is  an  excellent  and 
portable  instrument  for  preliminary  work,  having  a  fine 
needle  and  a  vernier  and  clamping  nut,  by  which  the 
sights  can  be  placed  at  an  angle  with  the  line  of  zeros, 
so  as  to  set  off  the  magnetic  declination  as  with  the 
Vernier  Compass  No.  226. 

The  instrument  has  folding  sights,  two  levels  and 
staff  mountings,  and  is  packed  in  a  mahogany  case. 


180-B     W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

We  make  two  sizes  of  the  Pocket  Vernier  Compass, 
having  needles  respectively  three  and  one  half  and  four 
and  one  half  inches  long.  In  the  smaller  instrument 
the  sights  have  a  slit  in  the  south  vane  and  a  hair  in  the 
north  vane,  for  readily  finding  an  object;  but  in  the 
larger  size  the  sights  are  made  half  slit  and  half  hair, 
as  shown  on  page  180-A.  Both  sizes  have  the  compass 
circle  graduated  to  half  degrees.  In  the  smaller  size 
the  vernier  of  the  variation  arc  reads  to  five  minutes, 
and  in  the  larger  size  to  single  minutes.  The  instru- 
ment may  be  used,  if  desired,  upon  a  light  tripod,  No. 
416,  No.  421  or  No.  426. 

When  ordered,  a  rack  movement  with  pinion  is 
added,  by  which  the  magnetic  declination  may  be  set  off 
more  readily.  , 

The  compass  with  three  and  one  half  inch  needle 
weighs  about  one  and  three  quarters  pounds;  that  with 
four  and  one  half  inch  needle  about  two  and  three 
quarters  pounds. 


LEVELING  INSTRUMENTS  181 

LEVELING  INSTRUMENTS 

ENGINEERS  WYE  LEVEL 

OF  the  different  varieties  of  leveling  instruments,  the 
Wye  Level  is  universally  preferred  by  American 
engineers  on  account  of  its  accuracy,  durability, 
ease  and  permanence  of  adjustment. 

We  manufacture  four  sizes  of  Wye  Levels,  having 
telescopes,  twenty-two,  eighteen,  fifteen,  and  twelve 
inches  in  length ;  the  smallest  size  is  called  the  Architects 
Level.  The  illustration  on  page  182,  represents  the 
two  largest  sizes. 

TELESCOPE.  The  telescope  has  near  its  ends  two 
rings  of  bell  metal  turned  truly  and  of  precisely  the 
same  diameter.  On  these  rings  it  rotates  in  the  wyes; 
or  it  can  be  clamped,  when  the  clips  of  the  wyes  are 
brought  down  upon  the  rings,  by  pushing  in  the  taper- 
ing pins. 

The  telescope  of  the  twenty-two  inch  and  eighteen 
inch  levels  has  a  pinion  movement  to  both  the  objective 
and  eyepiece  slides,  and  an  adjustment  for  centering  the 
eyepiece  slide,  shown  at  AA  in  the  sectional  view,  Fig. 
51,  page  183.  The  arrangement  for  insuring  the  accurate 
projection  of  the  objective  slide  is  also  shown  at  C,  in 
the  same  illustration.  Both  of  these  adjustments  are 
protected  from  disturbance  by  thin  cover  bands  which 
screw  over  them.  The  objective  slides  of  the  fifteen 
inch  and  the  twelve  inch  levels  have  pinion  movements 
but  the  eyepieces  have  spiral  or  screw  motions. 


182 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


K  W 

PH  PH 

O  O 

O  U 

02  02 

W  K 

^  A 

W  W 

H  H 

5  5 

G<1  00 

<N  rH 


H-l    H-l 


PS     PS 


5  2 
3  3 

55    5? 


co   co 

6   6 
fc  fc 


LEVELING  INSTRUMENTS 


183 


184         W.  &  L.  E.  GURLEY,  THOY,  NEW  YORK 

The  objective  slides  on  the  eighteen  and  twenty-two 
inch  Wye  Levels  are  fitted  with  our  improved  dust 
guard,  Fig.  2,  which  is  secured  to  the  main  telescope 
and  which  remains  stationary  while  the  slide  is  moved 
in  or  out,  thus  fully  protecting  it  against  injury  from 
any  outside  cause. 

SHORT  Focus.  The  telescopes  of  our  Wye  Levels, 
like  those  of  our  transits,  are  arranged  so  that  they  may 
be  focused  upon  an  object  much  nearer  the  instrument 
than  was  formerly  possible. 


FIG.  52 
No.  378  ENGINEERS  WYE  LEVEL 

15    INCH    TELESCOPE 

The  improvement  will  often  be  of  decided  advan- 
tage to  the  engineer.  Care,  however,  should  be  taken 
when  using  the  instrument  at  short  distances  to  correct 


LKVKLINO  INSTRUMENTS 


185 


the  level  vial  if  it  is  slightly  out  of  center  when  the 
instrument  is  thrown  out  of  balance  by  the  projection 
of  i In  slide. 

COMPASS.  A  compass 
witli  a  three  inch  needle  for 
obtaining  the  bearings  of 
lines  is  sometimes  attached 
to  the  telescope  in  such  a 
manner  as  to  be  readily 
removable  when  desired. 
I'ig.  5». 

HORIZONTAL  CIRCLE.  For 
laying  off  angles,  a  horizon- 
tal circle  three  and  one  half 
inches  in  diameter  can  be 
h'tted  to  the  leveling  head 
of  the  Wye  Level.  The 
circle  is  graduated  to  de- 
grees, and  J'H  rend  by  vernier 
to  five  minutes.  Fig.  58. 

Miititoit.  For  convenience,  in  oh.srrving  flu-  h-v.-l 
bubble,  a  mirror  can  be  attached. 

OIUKCTIVK  SLIDE.  The  interior  construction  of  the 
telescope  will  be  understood  from  the  sectional  view, 
Fig.  51,  page  188. 

The  adjustment  for  the  objective  slide,  which  is  a 
distinctive  feature  of  Gurley  instruments,  permits  the 


Fio.  58 

VIKW  OP  ENGINEERS  WVE 
LEVEL  EQUIPPED  WITH  A 
HORIZONTAL  CIRCLE,  A 
COMPASS,  AND  A  LEVEL 
lil/KHLK  MIRROR. 


186         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

accurate  projection  of  the  slide  throughout  its  whole 
range.  This  adjustment  makes  possible  the  alignment 
of  both  cross  wires  with  equal  accuracy,  which  could 
not  be  accomplished  without  it.  The  slide  is  always 
adjusted  in  the  process  of  manufacture  and  needs  no 
attention  from  the  engineer,  unless  the  instrument  is 
severely  injured. 

The  advantages  of  an  eyepiece  pinion  are  that  the 
eyepiece  can  be  moved  without  danger  of  disturbing  the 
telescope,  and  that  the  wires  are  brought  more  certainly 
into  distinct  view,  so  as  to  avoid  any  error  of  observa- 
tion arising  from  instrumental  parallax. 

LEVEL  VIAL.  The  level  tube,  with  ground  and  grad- 
uated vial  scale  is  attached  to  the  under  side  of  the 
telescope,  and  furnished  at  different  ends  with  the  usual 
movements  in  both  horizontal  and  vertical  directions. 

The  level  vial  F,  Fig  51,  is  a  glass  tube  with  an 
even  bore  from  end  to  end,  and  ground  on  its  inner 
surface,  so  that  the  run  of  the  air  bubble  may  be  uniform 
throughout  its  whole  range.  The  level  graduated  scale 
is  etched  on  the  glass. 

WYES.  The  Wyes,  Q,  of  our  levels  are  large  and 
strong,  of  hard  bronze,  and  each  have  two  adjustable 
capstan  nuts,  S.  The  clips  are  held  down  on  the  rings 
of  the  telescope  tube  by  the  Wye  pins,  which  are  taper- 
ing so  as  to  secure  the  rings  firmly.  The  clip  of  one  of 
the  Wyes  has  a  pin  projecting  from  it,  which,  entering 
a  recess  in  the  edge  of  the  ring,  insures  the  horizontal 
position  of  the  cross  wire. 


LEVELING  INSTRUMENTS  187 

LEVEL  BAR.  The  level  bar  is  round,  of  the  best  bell 
metal,  and  shaped  for  greatest  strength  in  the  parts 
most  liable  to  sudden  strains.  Connected  with  the 
level  bar  is  the  head  of  the  leveling  socket. 

SPINDLE.  The  instrument  is  supported  on  a  tapered 
steel  spindle  which  is  fitted  in  a  socket  extending  en- 
tirely through  the  leveling  head. 

SOCKETS.  Projecting  from  the  socket  are  four  arms, 
E,  heavily  ribbed  and  tapped  at  the  ends  to  receive  the 
leveling  screws.  The  leveling  screws  are  so  threaded 
that  they  fit  the  long  nuts  accurately,  and  have  caps 
protecting  the  threads  from  dust. 

BOTTOM  PLATE.  Attached  to  the  end  of  the  leveling 
socket  by  a  hemispherical  nut  is  the  bottom  plate  of  the 
leveling  head,  which  is  so  spaced  with  reference  to  the 
leveling  socket  that  it  pivots  easily  upon  it  with  the 
movement  of  the  leveling  screws. 

The  length  of  the  steel  spindle  and  the  wide  spacing 
of  the  leveling  screws  secure  stability  and  delicacy  of 
adjustment  for  the  most  accurate  work. 

LEVELING  HEAD.  The  leveling  head  is  similar  in 
construction  to  that  of  the  transit,  (see  page  42).  The 
tangent  screw  has  also  an  opposing  spring,  as  there 
described. 


188         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

ARCHITECTS  LEVEL 

The  Architects  Level  is  extensively  used  by  archi- 
tects, builders  and  millwrights  for  leveling  and  laying 
off  angles  of  foundations  for  buildings,  machinery, 
shafting,  etc.,  as  well  as  by  engineers  and  surveyors  for 
the  grading  of  streets,  sewers  and  drains. 

The  instrument  has  a  telescope  twelve  inches  in 
length,  furnished  with  rings  and  wyes  like  that  of  the 
larger  levels  and  is  adjusted  in  the  same  manner.  As 
now  made,  the  telescope  can  be  focused  upon  an  object 
six  and  one  half  feet  from  the  center  of  the  instrument. 

The  leveling  head  has  a  clamp  to  the  spindle,  and  a 
tangent  movement.  It  has  also  a  horizontal  circle  three 
inches  in  diameter,  fitted  to  the  upper  end  of  the  socket 
and  turning  readily  upon  it.  The  circle  is  graduated 
to  degrees,  figured  from  0  to  90  each  way,  and  is  read  to 
five  minutes  by  a  vernier  which  is  fixed  to  the  spindle. 

The  telescope  is  directed  to  any  object  by  hand,  the 
spindle  turning  readily  in  its  socket;  but  it  can  be 
clamped  in  any  position  by  the  clamp  screw  and  accur- 
ately pointed  by  means  of  the  tangent  screw. 

The  instrument  is  placed  either  upon  a  light  tripod 
or  on  a  small  triangular  plate  called  a  "trivet,"  having 
three  sharp  steel  points  by  which  it  is  firmly  set  upon 
any  surface.  Both  tripod  and  trivet  are  furnished  with 
the  level. 

A  sun  shade  is  also  supplied,  to  put  over  the  objec- 
tive to  protect  it  from  the  glare  of  the  sun. 


LEVELING  INSTRUMENTS  189 

ADJUSTMENTS.  The  adjustments  of  the  Architects 
Level  are  made  exactly  as  specified  in  the  description  of 
the  larger  levels.  They  are  not  liable  to  derangement, 
and  will  ordinarily  require  but  little  attention. 


FIG.  54 

No.  381  ARCHITECTS  LEVEL 
ONE  SIZE 

To  ADJUST  THE  WYE   LEVEL 

The  adjustments  which  are  common  to  all  Wye 
Levels,  and  with  which  the  engineer  should  be  fam- 
iliar, are: 

To  adjust  the  line  of  collimation,  or,  in  other  words, 
to  bring  the  intersection  of  the  cross  wires  into  the  longi- 
tudinal axis,  so  that  this  point  will  remain  on  any  given 
point  during  an  entire  rotation  of  the  telescope; 

To  bring  the  level  parallel  with  the  bearings  of  the 
wye  rings,  or  with  the  longitudinal  axis  of  the  telescope ; 


190         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

To  adjust  the  wyes  or  to  bring  the  level  into  a  posi- 
tion at  right  angles  with  the  vertical  axis  of  the  instru- 
ment. 

Before  beginning  the  adjustment  it  is  well  to  set 
the  cross  wires  approximately  horizontal.  This  adjust- 
ment cannot  be  accurately  made  until  the  other  adjust- 
ments are  completed. 

To  ADJUST  THE  LINE  OF  COLLIMATION.  Set  the 
tripod  firmly,  remove  the  wye  pins  from  the  clips  so  as 
to  allow  the  telescope  to  turn  freely,  clamp  the  instru- 
ment to  the  leveling  head,  and  by  the  leveling  and  tan- 
gent screws  bring  either  of  the  wires  upon  the  clearly 
marked  edge  of  some  object,  distant  from  one  hundred 
to  five  hundred  feet.  Then  with  the  hand  carefully 
rotate  the  telescope  half  way  around,  so  that  the  posi- 
tion of  the  same  wire  is  compared  with  the  object 
selected. 

Should  it  be  found  to  one  side  of  the  wire,  bring  it 
half  way  back  by  the  capstan  head  screws  at  right  angles 
with  it,  always  remembering  the  inverting  property  of 
the  eyepiece;  bring  the  wire  again  upon  the  object  and 
repeat  the  first  operation  until  it  will  reverse  correctly. 
Proceed  in  the  same  manner  with  the  other  wire  until 
the  adjustment  is  complete.  Should  both  wires  be 
much  out,  it  will  be  well  to  bring  both  nearly  correct 
before  either  is  finally  adjusted. 

When  this  is  effected,  unscrew  the  covering  of  the 
eyepiece  centering  screws,  shown  in  the  sectional  view 


LEVELING  INSTRUMENTS  191 

at  A  A,  page  183,  and  move  each  pair  in  succession  with 
a  screw  driver  until  the  wires  are  brought  into  the  center 
of  the  field  of  view.  The  inverting  property  of  the  eye- 
piece does  not  affect  this  operation,  and  the  screws  are 
moved  directly. 

To  test  the  correctness  of  the  centering,  rotate  the 
telescope  and  observe  whether  it  appears  to  shift  the 
position  of  an  object.  Should  any  movement  be  appar- 
ent, the  centering  is  not  perfectly  effected.  In  all 
telescopes  the  line  of  collimation  depends  upon  the  rela- 
tion of  the  cross  wires  and  objective,  and  therefore  the 
movement  of  the  eyepiece  does  not  affect  the  adjustment 
of  the  wires  in  any  respect. 

When  the  centering  has  once  been  effected  it  remains 
permanent,  the  cover  being  screwed  on  again  to  protect 
it  from  derangement. 

To  ADJUST  THE  LEVEL  VIAL.  Clamp  the  instrument 
over  either  pair  of  leveling  screws,  and  bring  the  bubble 
into  the  middle  of  the  tube.  Turn  the  telescope  in  the 
wyes  so  as  to  bring  the  level  tube  to  one  side  of  the 
middle  of  the  bar.  If  the  bubble  runs  to  the  end,  it 
indicates  that  the  vertical  plane  passing  through  the 
middle  of  the  bubble  is  not  parallel  with  that  drawn 
through  the  axis  of  the  telescope  rings. 

To  correct  the  error,  bring  the  bubble,  by  estimation, 
half  way  back  by  the  capstan  head  screws  on  each  side 
of  the  level  holder,  placed  usually  at  the  objective  end 
of  the  tube.  Again,  bring  the  level  tube  over  the  middle 
of  the  bar  and  the  bubble  to  the  middle,  turn  the  level 


192         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

to  either  side,  and,  if  necessary,  repeat  the  operation 
until  the  bubble  will  keep  its  position  when  the  tube  is 
turned  half  an  inch  or  more  to  either  side  of  the  middle 
of  the  bar. 

The  necessity  for  this  operation  arises  from  the  fact 
that,  when  the  telescope  is  reversed  end  for  end  in  the 
wyes  in  the  other  and  principal  adjustment  of  the 
bubble,  we  are  not  certain  of  placing  the  level  tube  in 
the  same  vertical  plane,  and  therefore  it  would  be  almost 
impossible  to  effect  the  adjustment  without  a  lateral 
correction. 

Having  now  largely  removed  the  initial  difficulties, 
we  proceed  to  make  the  level  tube  parallel  with  the 
bearings  of  the  wye  rings. 

To  do  this,  bring  the  bubble  into  the  middle  with  the 
leveling  screws,  and  then,  without  jarring  the  instru- 
ment, take  the  telescope  out  of  the  wyes  and  reverse  it 
end  for  end.  Should  the  bubble  run  to  either  end,  lower 
that  end,  or,  what  is  equivalent,  raise  the  other  by  turn- 
ing the  adjusting  nuts  on  one  end  of  the  level  until,  by 
estimation,  half  the  correction  is  made.  Again  bring 
the  bubble  into  the  middle  by  the  leveling  screws,  and 
repeat  the  whole  operation  until  the  reversion  can  be 
made  without  causing  any  difference  in  position  of  the 
bubble  in  the  bubble. 

It  would  be  well  to  test  the  lateral  adjustment  from 
time  to  time  during  this  operation  and  make  such  cor- 
rections as  may  be  necessary  in  that,  before  the  vertical 
adjustment  is  entirely  completed. 


LEVELING  INSTRUMENTS  193 

To  ADJUST  THE  WYES.  Having  made  the  previous 
adjustments,  it  remains  to  bring  the  level  into  position 
at  right  angles  with  the  vertical  axis,  so  that  the  bubble 
will  remain  in  the  middle  during  an  entire  revolution  of 
the  instrument. 

To  do  this,  bring  the  level  tube  directly  over  the 
middle  of  the  bar  and  clamp  the  telescope  in  the  wyes, 
placing  it  as  before,  over  two  of  the  leveling  screws. 
Unclamp  the  socket,  center  the  bubble,  and  turn  the 
instrument  half  way  around,  so  that  the  level  bar  may 
occupy  the  reverse  position  in  respect  to  the  leveling 
screws  beneath. 

Should  the  bubble  run  to  either  end,  bring  it  half 
way  back  by  the  wye  nuts  on  either  end  of  the  bar. 
Place  the  telescope  over  the  other  pair  of  leveling  screws, 
bring  the  bubble  again  into  the  middle,  and  proceed  as 
above  described,  changing  to  each  pair  of  screws  suc- 
cessively until  the  adjustment  is  very  nearly  perfected, 
when  it  may  be  completed  over  a  single  pair. 

When  the  level  has  been  thus  completely  adjusted, 
if  the  instrument  is  properly  made  and  the  socket  well 
fitted,  the  bubble  will  reverse  over  each  pair  of  screws 
in  any  position. 

This  adjustment  is  not  essential,  but  is  convenient. 
If  the  level  has  been  adjusted  parallel  to  the  line  of 
collimation,  the  line  of  sight  will  always  be  a  level  one 

if  the  bubble  so  indicates.  With  a  precise  level  this 
adjustment  is  not  made,  but  the  bubble  is  carefully 
viewed  at  the  time  of  sighting. 


194         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Should  the  engineer  be  unable  to  make  the  instru- 
ment work  correctly,  the  error  is  probably  caused  by 
some  injury  to  the  spindle  or  socket. 

In  such  case  the  instrument  should  be  sent  directly 
to  the  maker,  if  possible,  as  the  injury  may  require 
skilled  attention. 

The  adjustments  having  been  completed,  and  the 
instrument  being  precisely  level,  the  engineer  should 
rotate  the  telescope  in  the  wyes  until  the  pin  on  the  clip 
of  the  wye  will  enter  the  recess  in  the  ring  to  which  it  is 
fitted,  and  by  which  the  horizontal  position  of  the  cross 
wire  is  insured. 

When  the  pin  is  in  its  place,  the  horizontal  wire  may 
be  compared  with  any  level  line,  and  in  case  it  should 
not  be  parallel  with  it,  two  of  the  cross  wire  screws  that 
are  at  right  angles  with  each  other  may  be  loosened  and, 
by  the  screws  outside,  the  cross  wire  ring  turned  until 
the  wire  is  horizontal.  The  line  of  collimation  must 
then  be  corrected  again,  and  the  adjustments  of  the 
level  will  be  complete. 

To  ADJUST  THE  OBJECTIVE  SLIDE.  The  adjustment 
of  the  objective  slide  is  a  distinctive  feature  of  Gurley 
instruments  and  is  always  made  by  us  so  permanently 
as  to  need  no  attention  at  the  hands  of  the  engineer, 
unless  in  case  of  derangement  by  accident. 

In  making  this  adjustment,  it  is  necessary  to  remove 
the  level  tube  in  order  that  the  screw  immediately  above 
it  may  be  accessible. 


LEVELING  INSTRUMENTS  195 

To  adjust  the  objective  slide,  select  an  object  as 
distant  as  may  be  distinctly  observed,  and  upon  it  adjust 
the  line  of  collimation,  in  the  manner  described  on  page 
190,  making  the  intersection  of  the  wires  to  rotate  in 
the  wyes  without  passing  either  above  or  below  the  point 
or  line  selected.  In  this  position  the  slide  will  be  drawn 
in  nearly  as  far  as  the  telescope  tube  will  allow. 

With  the  pinion  head  then  move  out  the  slide  until 
an  object,  distant  about  ten  or  fifteen  feet,  is  brought 
clearly  into  view.  Again  rotating  the  telescope  in  the 
wyes,  observe  whether  the  wires  will  reverse  upon  this 
second  object. 

Should  this  be  the  case,  it  is  assumed  that,  as  the  line 
of  collimation  is  in  adjustment  for  these  two  distances, 
it  will  be  for  all  intermediate  ones,  since  the  bearings  of 
the  slide  are  true  and  their  surfaces  parallel  with  each 
other. 

If,  however,  either  or  both  wires  fail  to  reverse  upon 
the  second  point,  by  estimation,  remove  half  the  error 
by  the  screws  at  C  (Fig.  51,  page  183),  at  right  angles 
with  the  wire  to  be  corrected,  remembering  that,  on  ac- 
count of  the  inverting  power  of  the  eyepiece,  the  slide 
must  be  moved  in  the  direction  which  apparently  in- 
creases the  error.  When  both  wires  have  been  thus 
treated,  the  line  of  collimation  is  again  adjusted  on  the 
near  object,  and  the  telescope  again  brought  upon  the 
most  distant  point.  The  tube  is  again  rotated,  the 
reversion  of  the  wires  upon  the  object  once  more  tested, 
and  the  correction,  if  necessary,  made  in  the  same 
manner. 


196         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

EXPLORERS  LEVEL 

The  telescope  of  this  level  is  fastened  rigidly  and 
permanently  to  the  spindle  and  the  level  is  for  this 
reason  of  dumpy  design. 

This  small,  light  model  was  designed  to  meet  the 
requirements  of  engineers  for  a  compact  serviceable 
instrument  for  running  preliminary  lines  in  exploration 
work  where  it  is  not  convenient  to  operate  a  large 
instrument.  It  is  used  by  many  who  desire  an  accurate 
and  at  the  same  time  an  extremely  portable  level. 

The  Explorers  Level  is  a  companion  instrument  to 
our  Explorers  Transit  and  Explorers  Alidade,  and  can 
be  packed  with  them  in  an  ordinary  twenty-four  inch 
suit  case,  including  one  jointed  extension  tripod  as 
shown  on  page  59. 

To  ADJUST  THE  EXPLORERS  LEVEL.  By  means  of 
the  leveling  screws  and  the  nuts  at  the  ends  of  the  level 
vial,  adjust  the  level  until  the  bubble  will  remain  in  the 
center  when  the  instrument  is  rotated  on  the  spindle. 
Then  adjust  the  cross  wires  by  means  of  the  two  peg 
method  as  follows.  Drive  two  stakes,  opposite  sides  of, 
and  at  equal  distances  from,  the  instrument,  say  200 
or  300  feet.  Sight  on  a  rod  placed  consecutively  on 
each  stake.  Drive  the  highest  one  until  the  reading  on 
both  are  alike,  or  make  allowance  for  the  difference  in 
reading.  The  points  read  by  the  level  will  now  be  in 
the  same  horizontal  line,  however  much  the  telescope 
may  be  out  of  adjustment.  Remove  the  instrument  to 


LEVELING  INSTRUMENTS 


197 


a  point  less  than  50  feet  to  one  side  of  either  stake  and 
in  approximate  line  with  both.  Again  level  the  instru- 
ment and  note  the  heights  indicated  upon  the  rod  placed 
on  each  stake.  If  not  the  same,  adjust  the  cross  wires 
by  means  of  the  capstan  head  screws  over  nearly  the 
whole  error  on  distant  stake  and  repeat  until  the  read- 
ings on  both  stakes  are  alike. 


FIG.  55 
No.  384  EXPLORERS  LEVEL 

Bring  the  wires  into  the  center  of  the  field  of  view, 
by  centering  the  eyepiece  by  means  of  the  four  screws 
lettered  A  in  the  sectional  view  on  page  183,  which  does 
not  affect  other  adjustments,  and  the  instrument  is 
ready  for  use. 


198         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

To  USE  THE  LEVEL 

When  using  a  level,  the  legs  of  the  tripod  must  be  set 
firmly  into  the  ground,  and  the  bubble  brought  over  each 
pair  of  leveling  screws  in  turn  and  leveled  in  each  posi- 
tion, the  necessary  corrections  having  been  made  in  the 
adjustments. 

Care  should  be  taken  to  bring  the  wires  precisely 
into  focus,  and  the  object  distinctly  into  view,  so  that 
all  errors  of  parallax  may  be  avoided.  In  all  instances, 
the  wires  and  object  should  be  brought  into  view  so 
perfectly  that  the  cross  wires  will  appear  to  be  fastened 
to  the  surface,  and  will  remain  in  that  position  however 
the  eye  is  moved. 

In  running  levels  it  is  best,  wherever  possible,  that 
equal  fore  and  back  sights  should  be  taken,  to  avoid 
any  error  arising  from  the  curvature  of  the  earth,  and 
also  to  compensate  for  any  errors  of  adjustment  in  the 
instrument. 

To  USE  THE  ARCHITECTS  LEVEL 

The  instrument  having  been  carefully  leveled,  focus 
the  eyepiece  and  objective  upon  the  object  as  before 
described,  and  the  horizontal  cross  wire  will  give  any 
number  of  points  required,  which  will  all  be  in  the  same 
level  plane. 

A  board  held  erect  will  answer  as  a  rod,  and  "a  pencil 
line  drawn  across  it  at  the  place  cut  by  the  horizontal 
wire  will  give  the  height  of  the  starting  point.  Any 
different  points  on  the  rod,  either  above,  or  below  that 

.4.t  '.  :  •; •••...IA-;;I   .-     ,,, 


LEVELING  INSTRUMENTS 


199 


indicated  by  the  cross  wire,  will  show  the  difference  in 
height  of  the  various  points  observed,  as  compared  with 
the  starting  point. 

LAYING  OFF  ANGLES.  In  laying  off  angles  with  the 
Architects  Level,  the  bubble  should  first  be  brought  into 
the  middle  as  before  described,  and  the  vertical  cross 
wire  made  to  cut  the  object  or  line  from  which  the  angle 
is  to  be  taken.  Then,  the  spindle  being  clamped  by  the 
milled  head  screw  under  the  circle,  the  circle  is  turned 
around  by  hand  until  the  zero  lines  of  both  circle  and 
vernier  are  made  to  coincide.  Loosen  the  clamp  screw 
and  turn  the  telescope  to  the  point  desired,  and  the 
angle  between  the  two  points  will  be  read  off  on  the 
circle. 

By  the  use  of  the  vernier,  angles  can  be  read  on  the 
circle  to  five  minutes,  but  ordinarily  only  the  middle  line 
of  the  vernier  is  used,  and  the  angle  read  to  the  nearest 
degree. 

_  A     E  The  point  underneath  the  center  of 

the  instrument  is  indicated  by  the  point 
of  the  plummet  suspended  from  the 
leveling  head. 

In  many  cases,  after  the  walls  of  a 
building  have  been  carried  up  to  a  con- 
siderable height,  it  becomes  difficult  to 
set  up  the  tripod,  and  in  this 
case  the  level  is  screwed  upon 
the  trivet,  which  can  be  set 


APARTMENT  OF  CIVIL 


BERKELEY,  CALIFORNIA 


200         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

board  secured  to  the  building,  or  indeed  upon  any  sur- 
face nearly  level  and  not  less  than  six  inches  square. 

To  illustrate  the  value  of  this  instrument  in  laying 
out  the  sites  of  buildings,  suppose  it  is  desired  to  erect 
a  building,  C  D,  at  right  angles  with  a  building,  A  B, 
and  at  a  given  distance  from  its  front. 

First  set  up  the  level  at  E,  and  carefully  center  the 
bubble,  the  point  of  the  plummet  below  the  required 
distance  of  the  side  of  the  new  building  from  the  front, 
A  B.  Measure  the  same  distance  at  the  other  corner 
of  A  B,  and,  having  erected  the  rod,  sight  upon  it  with 
the  telescope  and  clamp  to  the  spindle. 

Now  carry  the  rod  the  required  distance  from  B, 
and  move  it  from  side  to  side  until  it  is  again  in  line 
with  the  telescope,  as  at  C. 

Remove  the  instrument,  and  having  carefully  set  it 
over  the  point  C,  by  the  plummet,  and  brought  the  bub- 
ble into  the  middle  as  before,  sight  the  telescope  again 
upon  the  rod  placed  at  E  or  F,  and  clamp  to  the  spindle. 
Bring  the  zeros  of  the  circle  and  vernier  to  coincide, 
unclamp,  and  turn  the  vernier  to  ninety  degrees;  this 
will  give  a  point,  D,  at  any  required  distance  from  C, 
and  C  D  will  be  the  side  of  the  proposed  building.  The 
side,  C  G,  is  determined  by  turning  the  telescope  around 
until  the  vernier  is  in  line  with  the  other  zero  of  the 
circle,  and  thus  the  corner,  C,  and  the  two  sides,  C  D 
and  C  G,  are  at  once  set  off,  and  the  remaining  corner, 
H,  easily  ascertained  by  making  D  H  and  G  H  equal 
to  C  G  and  C  D,  respectively. 


LEVELING  INSTRUMENTS  201 

Other  uses  of  the  level,  as  the  setting  of  floor  tim- 
bers, of  window  and  door  sills  and  the  leveling  of  floors, 
will  readily  occur  to  one  who  has  been  engaged  in  build- 
ing. To  the  millwright  such  a  level  is  almost  indispen- 
sable in  the  aligning  and  leveling  of  shafting,  in 
ascertaining  the  fall  of  water  obtainable,  and  in 
determining  the  overflow  of  land  by  a  mill  pond.  The 
farmer  will  find  it  of  value  in  locating  and  laying  out 
drains,  ascertaining  the  height  of  springs  and  similar 
work. 

This  level  has  become  widely  known,  and  its  sim- 
plicity, excellence  and  moderate  cost  have  created  a 
great  demand  for  it. 


202         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 
HAND  LEVELS 

FOR    RAILWAY     RECONNOISSANCE    AND    LOCATION,    AND 
WHEREVER   APPROXIMATE    LEVELING   IS    REQUIRED 

LOCKE  HAND  LEVEL.  This  instrument  consists  of 
a  brass  tube  about  six  inches  long,  having  a  level  vial 
on  top  near  the  object  end,  as  shown.  There  is  an 
opening  in  the  tube  beneath,  through  which  the  bubble 
can  be  seen,  as  reflected  by  a  prism  immediately  under 


FIG.  56 
No.  643  LOCKE  HAND  LEVEL 

the  level  vial.  Both  ends  of  the  tube  are  closed  by  disks 
of  plain  glass  to  exclude  dust,  and  there  is  at  the  inner 
end  of  the  sliding  or  eye  tube  a  semi-circular  convex 
lens,  which  serves  to  magnify  the  level  bubble  and  the 
cross  wire  beneath,  while  it  allows  the  object  to  be 
clearly  seen  through  the  open  half  of  the  tube. 

The  cross  wire  is  fastened  to  a  frame  moving  under 
the  level  tube,  and  adjusted  to  its  place  by  the  small 
screw  shown  on  the  end  of  the  level  case.  The  level  of 
any  object  in  line  with  the  eye  of  the  observer  is  deter- 
mined by  sighting  upon  it  through  the  tube,  and  bringing 
the  bubble  of  the  level  into  a  position  where  it  is  bisected 
by  the  cross  wire. 


LEVELING  INSTRUMENTS 


203 


ABNEY  LEVEL  AND  CLINOMETER.  The  Abney  Level 
is  a  modification  of  the  Locke  Hand  Level,  combining 
with  it  an  excellent  clinometer. 

The  main  tube  being  square,  it  can  be  applied  to 
any  surface,  the  inclination  of  which  is  ascertained  by 
bringing  the  level  bubble  into  the  middle,  and  reading 
off  the  angle  to  five  minutes  by  the  arc  and  vernier. 


FIG.  57 
No.  646  ABNEY  LEVEL 


When  sighted  at  an  object  and  the  bubble  brought  into 
the  middle,  the  vertical  angle  from  the  height  of  the 
eye  is  indicated.  When  at  zero  it  indicates  a  level  line. 

The  inner  and  shorter  arc  indicates  the  lines  of 
different  slopes,  the  left  edge  of  the  vernier  plate  being 
applied  to  the  lines,  and  the  bubble  brought  into  the 


204         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

middle  as  usual.  Graduations  can  also  be  furnished  to 
indicate  per  cent  of  grade.  A  small  compass,  with 
needle  about  one  and  one  half  inches  long,  is  sometimes 
attached  to  the  upper  surface  of  the  Abney  Level,  with 
a  plain  staff  socket  below. 


FIG.  58 
No.   640   MONOCULAR   HAND   LEVEL 

THE  MONOCULAR  HAND  LEVEL,  shown  in  No.  640, 
consists  of  a  tube  to  which  are  fitted  the  lenses  of  a 
single  opera  glass,  and  which  also  contains  a  reflecting 
prism,  a  cross  wire,  and  a  level  vial,  the  latter  being 
seen  in  the  open  part  of  the  tube. 

The  eye  lens,  as  indicated  in  the  illustration,  is  com- 
posed of  two  separate  pieces,  the  larger  one  being  the 
usual  concave  eye  lens  of  the  opera  glass,  and  the 
smaller  a  segment  of  a  plano-convex  lens  having  its 


LEVELING  INSTRUMENTS  205 

focus  on  a  cross  wire  under  the  level  vial  and  above  the 
reflecting  prism. 

The  observer  holds  the  tube  horizontal  with  the 
level  opening  uppermost,  and  observes  the  object  to 
which  the  instrument  is  directed,  and  the  position  of  the 
level  bubble  with  reference  to  the  cross  wire  on  the 
under  side  of  the  level  vial. 

When  the  hand  level  is  held  truly  horizontal  the 
cross  wire  will  bisect  the  bubble,  and  will  determine  the 
level  of  any  object  seen  through  the  telescope,  thus 
securing  to  the  observer  a  clear  view  of  the  object,  mag- 
nified by  the  telescope. 


206         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


LEVELING  RODS 

A  GOOD  Leveling  Rod  is  as  important  a  part  of  the 
essential  equipment  of  every  engineer  or  surveyor 
as  a  good  Transit  or  Level.     It  should,  therefore, 
be   selected   with   equal   care,   always   bearing   in   mind 
that  a  permanently  accurate  and  durable  rod  cannot  be 
obtained  at  a  low  price. 

Gurley  rods  have  steadily  grown  in  favor  with  dis- 
criminating users,  whose  experience  has  convinced  them 
that  the  greatest  satisfaction  under  varying  service 
conditions  can  be  obtained  with  these  rods.  With  the 
intention  of  having  Gurley  rods  absolutely  the  best  that 
can  be  made,  constant  study  and  experiments  are  carried 
on  and  no  expense  is  spared. 

A  good  rod  has  accurate  graduations,  retains  its 
straightness,  never  binds,  stands  the  hard  knocks  of 
field  use,  is  easy  to  read  and  stays  that  way  for  years. 
As  official  evidence  of  the  accuracy  of  Gurley  rods,  we 
are  prepared  to  submit  copies  of  reports  made  from 
tests  by  the  United  States  Bureau  of  Standards.  The 
rods  tested  were  furnished  from  our  regular  stock  to 
the  people  who  secured  the  certificates;  they  were  not 
selected  for  the  purpose. 

Gurley  rods  are  used  extensively  by  many  depart- 
ments of  the  U.  S.  Government  and  the  most  critical 
work,  necessitating  the  utmost  precision,  has  been  per- 
formed with  rods  of  our  manufacture. 


LEVELING  INSTRUMENTS  207 

SPECIAL  RODS.  Many  engineers  need  rods  of  special 
pattern,  graduation  or  shape  adapted  to  the  particular 
requirements  of  their  practice.  We  make  to  order  rods 
of  any  design  and  will  submit  estimates  of  cost  to  those 
who  desire  them  and  who  furnish  us  with  data  showing 
the  details  required. 

CONSTRUCTION 

THE  first  essential  in  the  manufacture  of  rods  is  the 
material,   and   experience   has    shown   that   certain 
localities  produce  wood  better  suited  for  this  pur- 
pose  than   others.     Our   expert  personally   examines   a 
large  quantity  of  the  lumber  and  selects  only  that  which 
straightness  of  grain  and  freedom  from  flaws  make  fit 
for   our   use.     The   peculiarities    of    grain   and   texture 
that  develop  in  the  different  woods  due  to  the  varying 
climatic  conditions  under  which  they  have  grown  must 
be  kept  in  mind  when  making  this  selection. 

The  blanks,  after  having  been  cut  to  the  desired 
sizes,  are  stored  and  carefully  air  dried  until  they  are 
thoroughly  seasoned.  Any  blank  that  warps  in  drying 
is  immediately  rejected. 

The  blanks  are  especially  treated  to  enable  the  rods 
to  withstand  the  varying  climatic  conditions  to  which 
they  will  be  subjected.  This  method  of  careful  prepar- 
ation and  inspection  is  expensive,  but  is  justified  by  the 
excellence  of  the  finished  product. 


208         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

GRADUATING.  The  engine  which  graduates  the  rods 
was  invented  and  built  in  the  Gurley  factory,  and  is  the 
result  of  years  of  experience  in  this  special  line  of 
work.  It  is  adapted  to  receive  and  graduate  all  kinds 
of  rods  accurately  in  the  decimal,  fractional  or  metric 
system,  and  in  any  other  system  which  may  be  desired 
for  special  use. 

On  Gurley  rods  the  graduations  are  not  merely 
printed  on  the  surface,  but  are  impressed  into  the  rod, 
thus  increasing  their  durability. 

Every  detail  is  carefully  observed  in  the  graduation 
of  the  rod;  the  engine  and  the  room  in  which  it  is  used 
are  so  arranged  that  they  are  kept  at  a  uniform  temper- 
ature, both  winter  and  summer.  The  bases  from  which 
the  graduations  are  made  are  linear  standards,  every 
division  of  which  has  been  verified  and  certified  by  the 
highest  authority  in  the  world  on  all  matters  pertaining 
to  Weights  and  Measures,  the  International  Bureau  of 
Weights  and  Measures,  Sevres,  France. 

FINISHING.  An  unusual  amount  of  attention  is  paid 
to  the  finishing  of  the  rods,  and  materials  are  used 
which  are  made  especially  for  us.  A  number  of  coats 
of  preservative  varnish  are  applied  and  rubbed  down 
•thoroughly.  Besides  being  noted  for  their  beautiful 
finish,  Gurley  rods  possess  unequaled  wearing  qualities. 

Wherever  possible,  the  exterior  corners  are  rounded, 
making  the  handling  or  carrying  of  the  rod  more  agree- 
able. With  the  improved  form  of  clamp,  the  slide  is 


LEVELING  INSTRUMENTS  209 

effectually  clamped  with  but  a   slight  pressure   of   the 
screw. 

THE  TARGETS  are  stamped  from  one  piece  of  metal 
and  have  a  raised  perimeter,,  or  rounded  rim,  which 
increases  the  strength  and  protects  the  face.  The 
targets  are  so  reinforced  that  the  screws  are  not  liable 
to  bend,  and  wherever  possible  the  use  of  nipples  is 
avoided,  as  they  often  work  loose. 

CARRYING  CASES.  To  prevent  the  defacing  of  the 
graduations  in  transportation,  a  canvas  case  to  hold  the 
rod  can  be  supplied.  This  case  is  substantially  made 
of  heavy  material  and  is  recommended  for  all  rods  used 
in  precise  leveling. 

REPAIRS  AND  REGRADUATING.  Owing  to  their  dur- 
able construction,  Gurley  rods  can  be  restored  at 
moderate  cost  to  first  class  condition  for  further  service, 
after  they  have  become  worn  or  damaged  by  excessive 
use  or  accident.  As  this  cannot  be  done  with  a  rod 
cheaply  made,  this  advantage  of  a  Gurley  rod  should 
be  considered  when  purchasing. 


210 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


PHILADELPHIA   ROD   No.   500 

This  Rod  is  made  in  two  parts, 
each  about  %  inch  thick  by  1  %  inch 
wide  and  7&  feet  long.  The  parts 
are  connected  by  two  metal  sleeves, 
the  upper  one  of  which  has  a  clamp 
screw  for  fastening  the  two  parts 
together  when  the  rod  is  extended 
for  a  higher  reading  than  7  feet. 
This  clamp  can  be  so  adjusted  as  to 
regulate  the  friction  on  the  rod. 

Both  faces  of  the  back  strip  and 
one  face  of  the  front  are  recessed 
ik  inch  below  the  edges.  These 
surfaces  are  painted  white,  grad- 
uated into  feet,  tenths  and  hun- 
dredths  of  a  foot,  and  the  feet  and 
tenths  figured.  The  graduations 
and  figures  are  slightly  impressed 
on  the  recessed  surfaces,  thus  in- 
creasing their  durability. 

The  front  piece  reads  from  the 
bottom  upward  to  7  feet,  the  foot 
figures  being  red  and  the  tenths 
figures  black.  When  the  rod  is  ex- 
tended to  full  length  the  front  sur- 
face of  the  rear  half  reads  from  7 
to  13  feet,  and  the  whole  front  of 
the  rod  is  figured  continuously  and 


LEVELING  INSTRUMENTS 


211 


becomes  a  self-reading  rod,  13  feet 
long,  reading  to  hundredths  of  a  foot. 

The  back  surface  of  the  rear  half 
is  figured  from  7  to  13  feet,  reading 
from  the  top  down.  It  has  a  ver- 
nier scale  by  which  the  rod  is  read 
to  thousandths  of  a  foot  as  it  is  ex- 
tended. The  target  has  a  raised 
perimeter  and  is  painted  in  white 
and  red  quadrants.  It  has  also  a 
vernier  scale  on  its  chamfered  edge, 
reading  to  thousandths  of  a  foot. 
The  target  has  a  micrometer  attach- 
ment which  permits  rapid  and 
accurate  setting. 

When  a  level  of  less  than  7  feet 
is  desired,  the  target  is  moved  up  or 
down  the  front  surface,  the  rod 
being  closed  and  clamped;  but  when 
a  greater  height  is  required  the  tar- 
get is  fixed  at  7  feet  and  the  rear 
half  extended,  the  vernier  scale  on 
the  back  giving  the  readings  like 
those  of  the  target  to  thousandths 
of  a  foot. 

SERVICE   ROD,  WITH   OVAL   TARGET, 
No.  500-R 

The  new  Service  rod  is  of  the 
standard  Philadelphia  type  and  sim- 
ilar to  our  No.  500  Rod,  but  with 
the  following  modifications:  It  is 
equipped  with  a  target,  oval  in 
form;  the  clamp  and  fixtures  are 
of  bronze,  the  screw  being  rein- 


212         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


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forced  and  protected  by  a  guard  and 
designed  for  easy  clamping, 
especially  when  wearing  gloves  or 
mittens  in  cold  weather;  the  finish 
is  not  quite  so  refined  as  that  of  our 
No.  500  Rod,  but  this  new  rod  will 
give  the  same  service  which  lias 
made  all  Gurley  rods  so  popular. 
In  general,  the  No.  500-R  Rod  will 
answer  every  requirement  in  point 
of  accuracy  and  service. 

500-B   PHILADELPHIA   ROD 

Many  engineers  desire  a  Phila- 
delphia Rod  which  can  be  directly 
read  at  a  maximum  distance  from 
the  instrument. 

Philadelphia  Rod  No.  500-B  is 
graduated  in  feet,  tenths,  and  half 
tenths  with  the  tenth  figures  0.06 
feet  high.  In  Fig.  61,  the  half 
tenth  graduations  are  not  shown. 

A  scale  on  the  target  and  on  the 
back  of  the  lower  section  enables 
the  rod  to  be  read  to  1/100  of  a 
foot.  This  rod  is  found  very  useful 
in  highway  and  railroad  cross  sec- 
tion work. 


LEVELING  INSTRUMENTS 


213 


No.    501    PHILADELPHIA    ROD 

IN   THREE   PARTS 

To  provide  a  rod  of  the  same  gen- 
eral design  and  use  as  the  Philadelphia 
rod,  but  capable  of  being  closed  to 
shorter  lengths,  we  supply  the  Phila- 
delphia rod  in  three  parts.  This  rod 
is  five  and  three  tenths  feet  long  when 
closed,  and  when  extended  reads  to 
thirteen  feet. 

In  reading  above  five  feet,  first  the 
rear  part  is  extended  to  its  full  length 
and  next  the  middle  piece,  the  readings 
being  made  on  the  graduated  edges  of 
the  rod  by  vernier  to  thousandths  of 
a  foot. 

When  fully  extended  the  front  sur- 
face becomes  a  self-reading  rod  to 
thirteen  feet,  the  graduations  being  to 
hundredths  of  a  foot. 

On  account  of  ease  in  transporta- 
tion, as  well  as  the  general  character 
and  excellence  of  this  rod,  we  believe 
it  will  be  approved  by  those  who  use  it. 


214          W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


PS 


No.  501-B   SELF   READING  ROD 

A  rod  which  is  very  popular  as 
a  long  self  reading  three  ply  Phila- 
delphia Rod  is  our  No.  501-B. 

This  rod  is  seven  and  six-tenths 
feet  high  when  closed  and  extends 
to  twenty  feet.  It  is  graduated  on 
four  faces  to  feet  and  tenths  and  on 
the  back  of  the  front  section  to  feet, 
tenths  and  hundredths.  It  reads 
by  two  scales  to  half  hundredths. 

The  target  is  of  aluminum  and 
the  rod  is  regularly  supplied  with  a 
canvas  carrying  case. 

MINING    RODS 

For  underground  operations  we 
are  prepared  to  furnish  two  ply 
standard  Philadelphia  Rods  like 
No.  500  or  Service  Rods  like 
No.  500-R  in  the  following  special 
lengths : 

3.3  feet  closed,  sliding  to  5  feet 
4.3  feet  closed,  sliding  to  7  feet 
5.3  feet  closed,  sliding  to  9  feet 


LEVELING  INSTRUMENTS 


215 


4    =  ^ 

CO 


No.  505  NEW  YORK  ROD 

This  rod  is  made  in  two  parts,  the 
pieces  sliding  one  on  the  other,  the 
same  end  being  always  held  on  the 
ground  and  the  graduations  starting 
from  that  point. 

The  graduations  are  made  to  tenths 
and  hundredths  of  a  foot,  the  tenth 
figures  being  black,  and  the  feet  marked 
with  a  large  red  figure. 

The  front  surface,  on  which  the 
target  moves,  reads  to  6%  feet  on  the 
two  part  rods.  When  a  greater  height 
is  required,  the  horizontal  line  of  the 
target  is  fixed  at  the  highest  gradua- 
tion, and  the  upper  half  of  the  rod 
carrying  the  target  is  moved  out  of  the 
lower,  the  reading  being  now  obtained 
by  a  vernier  on  the  graduated  side,  up 
to  an  elevation  of  12  feet. 

The  target  is  made  with  a  raised 
rim  to  strengthen  it  and  to  protect  it 
from  defacement.  It  is  arranged  with 
an  improved  clamp,  which  can  be  so 
adjusted  as  to  regulate  the  friction  on 
the  rod,  allowing  the  target  to  be  easily 
moved  up  and  down  or  to  be  clamped 
by  a  slight  turn  of  the  binding  screw. 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


The  face  of  the  target  is  divided 
into  quadrants  by  horizontal  and  ver- 
tical diameters,  the  quadrants  being 
painted  alternately  white  and  red,  or 
sometimes  white  and  black. 

The  opening  in  the  face  of  the 
target  is  nearly  two-tenths  of  a  foot 
long,  so  that  in  any  position  a  figure 
denoting  a  tenth  of  a  foot  can  be  seen 
on  the  surface  of  the  rod. 

The  vernier  on  the  right  hand  edge 
of  the  opening  is  graduated  into  ten 
equal  spaces  corresponding  to  nine 
hundredths  on  the  rod,  and  reads  to 
thousandths  of  a  foot.  The  gradua- 
tions start  from  the  horizontal  line 
which  separates  the  colors  of  the  face. 

The  rod  is  fitted  with  an  improved 
clamp  similar  to  that  on  the  target. 

ARCHITECTS  RODS  Nos.  510  AND  511 

Architects  Rod  No.  510  is  a  very 
light  and  simple  sliding  rod  made  in 
two  equal  parts,  each  %  incn  square, 
and  when  closed  the  rod  is  about  5  feet 
6  inches  long. 

As  shown,  the  face  of  the  front 
part  and  the  side  of  the  rear  part  are 
graduated  to  feet,  inches  and  sixteenths, 


LEVELING  INSTRUMENTS 


217 


2- 
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A     = 


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3- 
2- 


cc 


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and  read  by  an  index  on  the 
target  and  on  the  side  of 
the  rod. 

The  target  is  similar  to 
those  of  the  rods  already 
described,  and  moves  on  the 
closed  rod  when  levels  of 
less  than  5  feet  5  inches  are 
to  be  taken. 

When  a  greater  height  is 
needed,  the  target  is  fixed  at 
the  highest  graduation,  the 
rear  part  carried  above  the 
front  part  and  clamped  by 
the  clamp  screw  at  any  point 
desired,  and  the  height  up 
to  10  feet  read  off  by  the 
index  on  the  side  of  the 
lower  part. 

Architects  Rod  No.  511 
is  similar  to  No.  510  except 
that  the  face  of  the  front 
part  and  the  side  of  the  rear 
part  are  graduated  to  feet, 
tenths,  and  hundredths,  and 
read  by  verniers  on  the  tar- 
get and  side  to  thousandths 
of  a  foot. 

No.    517   SLIP- JOINTED 

LEVELING  ROD 

1920  Model 

This  rod  was  designed  for 
engineers  desiring  an  ex- 
tremely portable  leveling  or 


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218         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


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stadia  rod.  It  is  twelve 
feet  long  and  is  graduated 
on  a  surface  two  inches  wide 
to  feet,  tenths  and  hun- 
dredths.  The  two  joints 
are  secured  and  released  by 
spring  catches.  The  rod 
being  in  three  sections  is 
carried  in  a  canvas  case 
about  three  and  three  tenths 
feet  long. 

TELEMETER  OR  STADIA  RODS 
Nos.  514-B  TO  514-E 

No.  514-B  Stadia  Rod  is 
made  in  one  piece,  with- 
out target,  ten  feet  long, 
four  inches  wide,  with 
brass  ends  and  is  grad- 
uated on  recessed  face  of 
three  and  one-half  inches 
width  to  feet,  tenths  and 
hundredths. 

No.  514-C  Stadia  Rod  is 
similar  to  No.  514-B,  but 
twelve  feet  long. 

The  graduations  of  Nos. 
514-B  and  514-C  begin  at 
the  base  and  end  at  the 


LEVELING  INSTRUMENTS 


219 


top  of  the  rods.  The 
illustration  does  not  show 
completed  graduations. 

No.  514-D  Stadia  Rod  is 
made  in  one  piece,  with- 
out target,  ten  feet  long, 
three  and  one-eighth 
inches  wide,  with  brass 
ends  and  is  graduated  on 
flat  face  to  feet,  tenths 
and  two-one  hundredths. 

No.  514-E  Stadia  Rod  is 
similar  to  No.  514-D,  but 
twelve  feet  long. 

Stadia  Rods  Nos.514-B, 
514-C,  514-D,  or  514-E 
can  be  made  with  a  hinge 
joint  to  permit  folding, 
at  an  additional  cost. 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


7- 


TELEMETER  OR  STADIA  ROD 
No.  513 

This  Rod  is  formed  of  two  pieces 
of  pine,  each  two  and  one-half  inches 
in  width  and  6  feet  long.  The  inner 
surfaces  of  the  rod  are  recessed  and 
painted  white,  with  graduations  in 
black  to  feet,  tenths  and  hundredths, 
the  feet  figured  in  red  and  the  tenths 
in  black.  The  two  pieces  are  con- 
nected by  strong  brass  hinges  and  are 
folded  in  transportation.  When  in  use 
they  are  opened  and  are  held  firmly  in 
line  by  a  strong  metal  brace  and  clamp 
on  the  back  of  the  rod. 

The  rod  tapers  toward  the  top,  from 
a  thickness  of  1%  inches  at  the  bottom. 

This  is  a  self-reading  rod,  and  is 
often  used  in  connection  with  the  stadia 
to  ascertain  distances  by  simple  obser- 
vation, in  the  same  manner  as  the 
Philadelphia  Rod. 


84 

6 
5 


1- 


LEVELING  INSTRUMENTS 


221 


CROSS  SECTION  ROD,  No.  516 


This  Rod  is  made  of  well  seasoned 
pine,  and  is  ten  feet  long,  with  ends 
one  and  three-eighths  inches  thick  and 
two  inches  wide.  It  is  about  four 
inches  thick  at  the  middle,  where  there 
is  an  opening  for  the  hand,  as  shown. 
Both  sides  are  graduated  on  a  recessed 
white  surface,  the  graduations  being 
painted  black  like  those  of  a  leveling 
rod,  and  figured  from  the  end  of  the 
rod.  There  is  also  an  adjustable 
spirit  level  at  each  end,  as  shown  in 
the  illustration. 


PLAIN  LEVELING  RODS 
Nos.  518-A  TO  521-B 

These  self-reading  Rods  are  made 
of  seasoned  white  pine,  recessed  and 
graduated  on  one  face  like  the  Phila- 
delphia Rod.  A  rib  at  the  back,  ex- 
tending through  the  length  of  the  rod, 
gives  great  rigidity,  while  it  does  not 
materially  increase  its  weight. 


222 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


They  are  furnished  in  lengths  varying  from  ten  to 
sixteen  feet  and  the  ten  foot,  twelve  foot  and  fourteen 
foot  rods  are  made  either  in  one  piece  or  with  a  hinged 
joint.  The  sixteen  foot  rod  is  made  only  with  a  hinged 
joint. 


FIG.  73 
VIEW  OF  HINGED  JOINT 


Note  the  sturdy  construction  of  the  hinges  and  the 
manner  in  which  the  strong  metal  brace  is  anchored 
into  the  wooden  rib;  also  the  wing  nut  clamp  screw. 


LEVELING  INSTRUMENTS 


223 


• 


PLAIN   LEVELING   ROD 

IN    FOUR   PARTS 

No.   524-A 

This  is  a  simple  form  of  self-read- 
ing rod  in  four  parts,  very  light  and 
compact,  capable  of  extension  to  eleven 
and  two-tenths  feet,  and  reading  to 
hundredths  of  a  foot.  This  same  form 
of  rod  is  also  made  in  two  parts,  ex- 
tending to  ten,  twelve,  or  fourteen  feet. 
See  Nos.  522-A,  B  and  C. 


224         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


LEVELING  INSTRUMENTS 


225 


B 


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->  cc 
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g 


GURLEY    PRECISE    ROD, 
MOLITOR  PATTERN 

The  Precise  Leveling  Rod, 
Molitor  Pattern,  as  shown 
on  page  224,  is  of  T-shaped 
section,  12  ft.  long,  and  is 
graduated  to  feet,  tenths 
and  hundredths.  It  can  be 
graduated  to  millimeters,  if 
desired.  It  is  equipped 
with  a  circular  level,  two 
wooden  handles,  a  plumb- 
ing attachment  and  plum- 
met, an  enclosed  thermome- 
ter, a  canvas  case  and  a 
turning  point.  It  is  packed 
in  a  special  pine  box  with 
hinged  cover,  handles  and 
lock. 

GURLEY   SELF-READING 
TAPE     LEVELING     ROD 

The  Tape  Rod  is  a  self- 
reading  rod  of  decidedly 
different  design  from  the 
Philadelphia  Rod.  It  is  a 
wooden  rod,  made  in  one 
piece  with  a  metal  roller  set 
in  it  near  each  end.  Pass- 
ing over  these  rollers  is  a 
continuous  steel  band  twenty 
feet  long  and  one-tenth  foot 
wide,  on  the  outside  of 
which,  for  its  entire  length, 


liJU 


226         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

is  painted  a  scale  graduated  to  feet,  tenths  and  half- 
tenths,  with  the  details  of  the  numbers  so  designed  that 
readings  to  the  nearest  one-hundredth  of  a  foot  can 
readily  be  read. 

It  is  provided  with  a  clamp  so  that  the  metal  band, 
or  tape,  can  be  set  at  any  desired  reading  and  held  firmly 
in  that  position. 

Where  there  are  a  large  number  of  elevations  to 
be  calculated,  it  will  save  much  time  to  use  a  tape 
rod  which  is  so  arranged  that  no  elaborate  figuring 
is  required.  In  this  rod,  the  numbers  increase  from 
the  top  toward  the  bottom,  the  opposite  way  from 
ordinary  rods.  The  level  is  set  up  at  a  conven- 
ient point  and  the  rod  held  on  a  bench  mark.  The 
tape,  or  band,  on  the  rod  is  then  moved  up  or  down  as 
directed  by  the  levelman  until  he  reads  the  feet,  tenths 
and  hundredths  which  are  the  same  as  those  of  the 
elevation  of  the  benchmark,  e.  g.,  if  the  elevation  of  the 
B.  M.  is  195.62,  the  tape  will  be  moved  until  it  reads 
5.62.  If  the  rod  is  then  held  on  a  point  1.61  feet  lower 
than  the  bench,  the  rod-reading  will  be  4.01,  since  with 
this  rod  the  readings  decrease  as  the  rod  is  lowered. 
The  elevation  of  the  point  is  then  194.01  feet,  or 
sufficiently  precise  for  topographic  work,  194.0  feet. 
In  this  way  the  elevations  are  read  directly  on  the  rod 
to  feet  and  decimals  of  feet,  the  tenths  and  hundredths 
of  feet  being'  supplied  mentally.  Obviously  the  only 
notes  kept  are  the  columns  of  stations  and  elevations. 

The  rod  is  10  ft.  8l/>  inches  long  and  graduated  on 
one  edge  to  feet  and  tenths.  A  canvas  case  can  be 
supplied  for  the  above  rod. 


LEVELING  INSTRUMENTS 


227 


FIG.    82.     GURLEY   PRECISE   LEVELING  ROD   No.   550-R 


228         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

GURLEY  PRECISE  ROD 
WITH  TURNING  POINT  AND  PLATE 

The  Precise  Leveling  Rod,  as  shown  on  page  227, 
is  made  in  the  cross-shaped  section  and  is  graduated  on 
three  faces  to  yards,  tenths  and  hundredths.  It  reads 
to  3^/2  yards,  and  has  silver-faced  plugs  at  each  half 
yard  enabling  it  to  be  checked  to  a  steel  tape  of  standard 
length.  It  is  fitted  with  wooden  handle,  thermometer, 
and  fixed  circular  rod  level.  In  addition  there  is  a 
canvas  case  and  a  turning  point  and  plate,  all  neatly 
packed  in  a  special  pine  box  with  hinged  cover,  handles 
and  lock. 


LEVELING  INSTRUMENTS 


229 


FLEXIBLE   OR   POCKET   LEVELING   RODS 

The  flexible  self-reading  rod  is  a  convenient  form 
where  extreme  accuracy  is  not  essential  and  where  ease 
in  carrying  is  desirable.  It  is  made  of  specially  pre- 
pared canvas,  so  treated  as  to  insure  permanence  in 
length  within  reasonable  limits,,  and  is  graduated  on  its 
painted  surface  to  feet,  tenths,  and  hundredths,  or  to 
special  design.  In  use  it  is  fastened  to  a  board  with 
thumb  tacks,  and  can  be  rolled  up  easily  and  carried  in 
the  pocket  in  tin  case  with  which  it  is  provided. 


FIG.  83 
Nos.  525-B  TO  528 

FLEXIBLE  OR  POCKET  LEVELING  RODS 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


cc 

IQ 

c 

r: 

id 

6 

X 


METRIC   RODS 

Besides  the  usual  gradua- 
tion of  leveling  rods  into  feet 
and  parts  of  a  foot,  we  grad- 
uate them,  when  desired,  into 
meters,  decimeters  and  centi- 
meters, without  extra  charge. 

The  scales  on  the  targets 
and  sides  of  the  rods  read  the 
centimeters  to  millimeters  on 
all  except  the  Telemeter,  Tel- 
escopic and  Plain  Rods,  which 
have  no  targets  and  are  read 
only  to  centimeters.  The  New 
York,  and  Architects  metric 
rods  are  graduated,  when  de- 
sired, to  read  by  vernier  to 
one-tenth  of  a  millimeter. 

COMBINED  LEVELING  POLE  AND 
FLAGSTAFF   Nos.   530  AND  531 

The  Leveling  Pole,  No.  530, 
is  a  combination  of  a  plain 
self-reading  rod  and  a  flagstaff. 
It  is  made  with  flat  face,  front 
and  rear,  and  rounded  sides. 
One  face  is  graduated  to  feet 
and  hundredths  of  a  foot, 
while  the  other  face  and  sides 
are  graduated  to  feet  only  and 
are  painted  red  and  white 
alternately. 


LEVELING  INSTRUMENTS  231 

The  pole  is  made  7  and  9  feet  long,  the 
graduated  faces  reading  to  6  and  8  feet, 
respectively,  and  when  used  as  a  rod  is  read 
as  shown  in  the  illustration. 

WOODEN  FLAGSTAFFS   Nos.   534   TO   538-B 
w  Wooden    Flagstaffs,    or    Ranging    Poles, 

o  Nos.  534  to  536  are  made  in  three  sizes  and 

^  are  octagonal  in   form,    tapering    from    the 

£  bottom  to  the  top,  and    have    metal    shoes. 

g  They  are  graduated  to  feet,  and  painted  al- 

<  ternately  red  and  white.     When  desired  they 
are  graduated  metrically,  five  spaces  to  each 

w  meter. 

J  Jointed  Wooden  Flagstaffs  Nos.  537-A  to 

P  538-B  are  especially  designed  for  convenience 

fc  in  use  and  for  ease  in  carrying  when  travel- 

^  ing.     They  are  about  1  inch  in  diameter,  and 

§  are  made  in  equal  length  sections,  which  are 

•-1  firmly  joined  together    by    protected    metal 

5  screw  joints.        If  desired,  a  heavy  canvas 

*°  case  is  furnished  to  contain  the  several  parts, 

H  and  to  protect  them   from  injury  in  trans- 

<!     portation.     See  illustration  on  page  232. 

o 

g  IRON  AND  STEEL  RANGING  POLES 

^  Nos.  540-A  TO  544 

£  Ranging  Poles  Nos.  540-A  to  540-B  are 

made  in  two  lengths,   of  a   solid  hexagonal 
co     steel  rod,  %  in.  in  diameter,  are  graduated  to 
feet  and  are  painted  alternately  red  and  white. 
Ranging  Poles  Nos.  541  to  544  are  made 
of  an  iron  tube,  it  inch  in  diameter,  in  three 
lengths,  are  graduated  to  feet  and  are  painted 
alternately  red  and  white. 

Any  of  the  above  staffs  and  poles  can  be  fur- 
nished with  metric  graduations  (5  to  a  meter). 


232         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


SCREW-JOINTED    WOODEN    FLAGSTAFFS 


FIG.  87.     Nos.  537-A  TO  538-B  FLAGSTAFFS 

The  above  illustration  shows  Flagstaff  No.  537-D, 
6  feet  in  length,  in  3  sections  of  2  feet  each,  having 
protected  metal  screw  joints.  The  heavy  canvas  case, 
for  protecting  the  rod  from  injury  in  transportation, 
also  is  shown. 


LEVELING  INSTRUMENTS  233 


GURLEY  ROD  LEVELS 

We  make  four  patterns  of  Rod  Levels  for  the  accur- 
ate plumbing  of  leveling  rods  and  ranging  poles. 

No.  545  is  adaptable  to  any  rod.  It  is  held  in  place 
by  the  hand  or  it  may  be  secured  by  a  string  or  rubber 
band  snapped  over  hooks  attached  to  each  plate  of  the 
level. 


I 


FIG.  88.     No.  545  ROD  LEVEL  AS  APPLIED  TO  A  ROD 


234         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

No.  546  has  a  circular  level  vial,  which  folds  against 
the  rod  when  not  in  use.  This  level  is  attached  perma- 
nently to  the  rod  and  cannot  be  used  where  there  is  a 
target  or  clamp  band  to  slide  past  it.  It  is  intended 
for  rods  made  of  one  piece,  and  also  for  those  which 
fold. 


FIG.  89.     No.  546  ROD  LEVEL 


LEVELING  INSTRUMENTS 


235 


GURLEY  ROD  LEVELS 

For  use  with  Precise  Rods  where  greater  accuracy 
and  ease  of  observation  are  required,  we  recommend 
Rod  Level  No.  54*7. 

The  case,  with  vial  30  millimeters  in  diameter,  is 
supported  on  a  bracket  which  may  be  securely  attached 
to  the  rod.  Three  screws  fasten  the  case  to  the  bracket 
and  provide  means  of  ready  adjustment. 


FIG.  90.     No.  547  ROD  LEVEL 


236 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


No.  548  has  an  aluminum  frame  and  is  so  made  that 
it  can  be  used  on  sliding  rods  such  as  Nos.  500  to  505. 


FIG.  91.     No.  548  ROD  LEVEL 

NOTE — All  circular  Rod  Levels  have  one-piece  her- 
metically sealed  vials  which,  unless  broken,  will  not 
leak.  This  feature  overcomes  a  serious  defect  in  cir- 
cular levels  made  of  two  pieces  of  glass  and  which 
cannot  be  guaranteed  against  leakage  or  evaporation. 


LEVELING  INSTRUMENTS  237 


ANGLE  TARGETS 

Angle  targets,  extending  over  the  graduated  face  and 
one  side  of  the  rod,  can  be  supplied  with  Rods  Nos. 
500-R,  500-B,  501,  502-A  and  505,  instead  of  the  regular 
target,  at  an  extra  cost. 

MICROMETER   TARGETS 

Micrometer  Targets,  similar  to  the  target  shown  with 
Philadelphia  Rod  No.  500  on  page  210,  can  be  supplied 
with  Rods  Nos.  500-R,  500-B,  501,  502-A  and  505, 
instead  of  the  regular  target,  at  an  extra  cost. 

ANGLE   MICROMETER   TARGETS 

Angle  Micrometer  Targets  can  be  supplied  with  Rods 
Nos.  500-R,  500-B,  501,  502-A  and  505,  instead  of  the 
regular  target,  at  an  extra  cost. 

REPAIRING    AND    REGRADUATING    RODS 

Old  and  worn  rods  need  not  be  discarded,  as  they 
can  be  repaired  and  regraduated.  We  have  unequaled 
facilities  and  our  method  is  such  that  when  the  work  is 
done,  the  rods  are  as  good  for  service  as  they  were 
when  new. 

The  average  cost  of  repainting  and  regraduating 
two-ply  rods,  such  as  No.  500  and  No.  505,  varies  from 
$4.50  to  $7.00.  These  prices  include  new  parts  such 
as  clamp  screws,  etc.,  which  are  frequently  required. 

Estimates  for  repairing  other  patterns  will  be  sub- 
mitted upon  request. 


238         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

GURLEY  TRIPODS 

The  legs  of  all  Gurley  Tripods  are  made  of  straight 
grained  hardwood,  and  are  about  4  feet  8  inches  long 
from  head  to  point.  The  upper  part  of  the  leg  is 


FIG.  92 

Nos.  415  AND  416  Nos.  400  AND  430 

SOLID  ROUND  LEG  TRIPODS      SOLID  ROUND  LEG  TRIPODS 
FOR  COMPASSES  FOR  TRANSITS  AND  LEVELS 

flattened  and  slotted  to  fit  closely  on  each  side  of  a  tenon 
projecting  from  the  under  side  of  the  tripod  head,  to 


LEVELING  INSTRUMENTS 


239 


which  it  is  firmly  held  by  a  brass  bolt,,  with  large  head 
and  thumb  nut  on  opposite  sides  of  the  leg.  The  tripod 
head  is  of  the  best  bronze  metal,  the  tenons  and  upper 


FIG.  93 

Nos.  405  AND  435  Nos.  410  AND  440 

SPLIT  LEG  TRIPODS  EXTENSION    LEG    TRIPODS 

FOR  TRANSITS  AND  LEVELS  FOR  TRANSITS  AND  LEVELS 

part  being  cast  in  one  piece.  The  point  or  shoe  is  a 
tapering  ferrule,  having  an  iron  end.  It  is  cemented 
and  firmly  riveted  to  the  wood. 


240         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

SOLID  ROUND  LEG  TRIPODS.  These  are  made  in 
three  sizes,  as  follows:  Tripod  No.  400,  the  heavy  size, 
has  a  metal  head  4*4  inches  in  diameter,  with  legs  1% 
inches  in  diameter  at  the  top,  1%  inches  at  the  swell 
and  ll/g  inches  near  the  point.  This  pattern  is  suitable 
for  use  with  the  Precise  Transits  Nos.  6-A  to  10-A  and 
No.  18-A,  and  with  the  Engineers  Wye  Levels,  but, 
unless  otherwise  ordered,  we  regularly  supply  Split  Leg 
Tripods  Nos.  405  and  435  with  these  instruments. 

Tripod  No.  415,  the  medium  size,  has  a  head  about 
3  inches  in  diameter,  and  legs  which  are  about  1  inch  in 
diameter  at  the  top,  1%  inches  at  the  swell  and  % 
inch  near  the  point.  This  tripod  is  designed  for  use 
with  Vernier  Compass  No.  226. 

Tripod  No.  416,  the  small  size,  is  for  use  with 
Pocket  Compasses.  It  is  of  the  same  pattern  as  No. 
415,  but  has  a  smaller  head  and  legs.  The  legs  are 
nearly  %  inch  in  diameter  at  the  top  and  bottom,  and 
1%  inches  at  the  swell. 

SPLIT  LEG  TRIPODS.  The  form  of  the  improved  Split 
Leg  Tripods,  Nos.  405  and  435,  is  shown  in  section  at 
A-B  in  the  illustration. 

The  legs  are  of  straight  grained  hardwood,  combin- 
ing stiffness  and  strength  with  reduced  weight,  and 
allowing  greater,  ease  in  carrying.  Several  sizes  of  this 
tripod  are  made  for  use  with  transits,  levels  and  com- 
passes. 

EXTENSION  LEG  TRIPODS,  Nos.  410  and  440,  shown 
in  section  at  A-B,  are  very  popular,  as  they  combine 


LEVELING  INSTRUMENTS 


241 


strength  and  rigidity  with  light  weight  and  are  especially 
easy  and  convenient  to  carry.  The  shape  of  the  side 
pieces  allows  the  middle  piece  to  be  clamped  firmly  with 
the  bands  and  screws,  while  slight  changes  in  length  can 
be  made  by  twisting  the  middle  piece  up  or  down.  In 
carrying,  the  points  are  usually  reversed  in  position, 
and  the  total  length  is  reduced  to  thirty-eight  inches. 


FIG.  94- 

Nos.  412  AND  443  JOINTED  EXTENSION  LEG  TRIPODS 
FOR  EXPLORERS  TRANSITS  AND  LEVELS 


242         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

These  tripods  are  made  in  several  sizes.  The  large 
size  is  used  with  the  large  transits  and  levels,  and  the 
medium  size  with  the  Light  Mountain  Transits.  A 
smaller  size  is  used  writh  the  smaller  transits,  Architects 
Level  and  large  compasses.  The  smallest  size  is  used 
with  the  Pocket  Compasses. 

For  use  in  mines,  which  have  shallow  veins  or  seams, 
we  are  prepared  to  furnish  special  extension  tripods 
which  have  a  minimum  height  of  about  twenty-two  inches 
and  a  maximum  height  of  about  thirty-six  inches.  The 
price  is  the  same  as  for  tripods  of  full  size. 

JOINTED  EXTENSION  LEG  TRIPODS.  For  use  with 
Explorers  Transits  Nos.  20-A  to  24-A  and  Explorers 
Level  No.  384  we  furnish  a  special  light  weight  tripod, 
each  leg  of  which  has  a  protected  metal  screw  joint  in 
addition  to  the  extension  feature.  The  minimum  length 
when  assembled  for  carrying  is  only  twenty-four  inches, 
so  that  it  can  be  packed  in  an  ordinary  size  suitcase. 
A  leather-trimmed  canvas  carrying  case,  with  handle, 
is  furnished. 

CARRYING  CASES  FOR  TRIPODS 

To  protect  the  tripod  in  transportation,  a  carrying 
case  can  be  furnished.  One  style  of  case  is  substantially 
made  of  heavy  canvas,  with  leather  trimmings.  Another 
form  is  made  of  sole  leather,  with  cap  and  carrying 
handle. 


PLANE  TABLES  243 


THE  PLANE  TABLE  OUTFIT 

THE  PLANE  TABLE  OUTFIT  consists  of  a  drawing 
board  to  hold  the  paper,  supported  on  a  tripod  so  that 
it  may  be  leveled,  a  level  vial,  compass,  and  alidade  or 
combined  sight  and  ruler. 

THE  DRAWING  BOARD  is  built  up  to  prevent  warping. 
For  use  in  some  localities,  as  the  Philippine  Islands, 
cleats  are  screwed  to  the  underside.  The  screws  pass 
through  the  cleats  in  oblong  slots  with  metal  bushings 
which  fit  closely  under  the  heads  but  allow  the  screws 
to  move  freely  when  drawn  by  the  contraction  or  expan- 
sion of  the  board,  caused  by  climatic  conditions.  The 
paper  is  held  firmly  by  brass  screws  passing  through 
the  edges  of  the  paper  into  brass  sockets  let  into  and 
slightly  below  the  surface  of  the  board.  This  method 
offers  no  obstruction  to  the  movement  of  the  alidade 
about  the  surface  of  the  board. 

COMPASS.  A  square  brass  plate  with  a  magnetic 
compass  and  levels  is  used  for  leveling  and  orienting  the 
board  and  if  placed  against  the  edge  of  the  alidade  gives 
the  magnetic  bearing.  Another  form  is  a  trough  com- 
pass either  inserted  in  the  edge  of  the  board,  or  mounted 
on  the  alidade  blade,  with  a  circular  level  on  the  blade 
of  the  alidade. 

THE  PLUMBING  ARM,  shown  in  the  illustration  on 
page  2 44,  is  equipped  with  an  index  that  may  be  brought 
to  a  given  place  on  the  paper,  the  plummet  hanging  to 
it  indicates  the  corresponding  point  on  the  ground. 


24,4,         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


THE   JOHNSON   MOVEMENT 

Plane  Tables  are  generally  mounted  on  the  Johnson 
Plane  Table  Movement,  which  has  been  adopted  as 
standard  equipment  by  the  U.  S.  Geological  Survey  and 
by  many  State  Geological  Departments.  The  construc- 
tion of  the  Johnson  Movement  is  shown  in  the  cut  on 
page  245.  It  consists  of  a  ball  and  socket  head  with 
an  inner  spindle.  Loosening  the  upper  nut  A  allows 
the  board  to  be  leveled  in  any  direction,  to  orient  the 
board  loosen  the  lower  nut  B. 


FIG.  95 

No.  576-C  PLANE  TABLE  OUTFIT,  WITH  JOHNSON 
MOVEMENT  No.  570,  STANDARD  TELESCOPIC  ALI- 
DADE No.  584-C,  AND  24"  x  31 "  DRAWING  BOARD 
No.  573. 


PLANE  TABLES 


245 


PLANE  TABLE 

The  Plane  Table  method  of  map  making  and  sur- 
veying is  rapidly  increasing  in  popularity  as  its 
principles  and  advantages  are  becoming  better  under- 
stood. On  account  of  their  combined  efficiency  and 
portability,  the  several  Gurley  Instruments  designed 
especially  for  this  class  of  work  "have  become  standard 
equipment  with  the  principal  users  of  Plane  Table 
Outfits.  This  method  consists  of  locating  graphically 
on  a  map,  at  the  time  of  the  survey,  the  points  desired, 


FIG.  96 

No.  570  JOHNSON  PLANE   TABLE  MOVEMENT, 
WITH  SPLIT  LEG  TRIPOD 


246         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

no  other  notes  or  figuring  being  required.  Points  are 
located  either  by  intersecting  lines  sighted  from  different 
stations,  by  tape  measurement,  or  by  stadia. 

Since  the  map  is  made  in  the  field  where  everything 
can  be  viewed,  the  likelihood  of  omitting  necessary  de- 
tails is  reduced,  most  of  them  can  be  put  in  with  but 
little  work.  This  method  avoids  the  necessity  of  taking 
notes,  of  reading  horizontal  angles  and  the  calculation 
of  the  same.  It  is  very  easy  to  detect  errors,  since 
checking  is  accomplished  by  simply  sighting  on  a  given 
point  from  various  stations.  It  is  more  rapid  than 
ordinary  methods  of  transit  surveying,  particularly 
where  much  topographical  detail  is  desired. 


FIG.  97 

No.  584-C  TELESCOPIC  ALIDADE,  WITH  DETACHABLE 
STRIDING   LEVEL,   EDGE   GRADUATED  VERTICAL   ARC 

COMBINED     WITH     BfiAMAN     STADIA     ARC,     CIRCULAR 

LEVEL,  AND  TROUGH  COMPASS. 


PLANE  TABLES  247 


Two  sizes  of  the  Johnson  Movement  are  made.  No. 
570  is  the  regular  size,  used  with  the  larger  boards,  and 
No.  571,  a  special  light  weight  model  generally  used 
with  the  smaller  boards  and  the  Explorers  Alidade 
No.  592-C.  Any  of  the  alidades,  however,  can  be  used 
with  the  Johnson  Plane  Table. 

TELESCOPIC  ALIDADES 

ALIDADE  No.  584-C  has  a  brass  ruler  eighteen  inches 
long  and  three  inches  wide,  with  the  edge  beveled.  On 
this  blade  is  mounted  a  circular  spirit  level,  the  glass 
body  of  which  is  hermetically  sealed,  and  which  is  sensi- 
tive enough  to  permit  the  plane  table  to  be  leveled  with 
sufficient  accuracy.  Attached  also  to  the  ruler  is  a 
trough  compass  having  a  four  inch  needle,  and  whose 
meridian  line  is  parallel  to  the  fiducial  edge.  If  desired, 
the  trough  compass  can  be  omitted  from  the  blade  and 
be  furnished  separately  for  insertion  along  one  edge  of 
the  drawing  board. 

The  telescope,  which  is  mounted  on  a  column  attached 
to  the  ruler,  is  eleven  inches  long,  and  is  equipped  with 
an  enlarged  objective,  platinum  cross  wires  and  stadia 
wires,  and  a  detachable  striding  level  with  revolving 
shield.  The  telescope  is  regularly  furnished  with  an 
inverting  eyepiece,  and  is  fitted  with  a  diagonal  prism. 
(If  an  erecting  eyepiece  is  desired,  it  can  be  had  with 
Alidade  No.  584-B,  which  is  otherwise  similar  to  Ali- 
dade No.  584-C,  except  that  the  telescope  does  not  have 
an  enlarged  objective.)  For  easy  adjustment  of  the 
line  of  collimation,  the  telescope  can  be  revolved  on  its 


248         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

longitudinal  axis  through   180  degrees.     The  telescope 
axis  is  equipped  with  clamp  and  tangent  movement. 

The  vertical  arc  is  graduated  on  sterling  silver  and 
reads  by  vernier  to  one  minute.  For  convenience  in 
reading  the  point  of  zero  deflection  is  marked  30°  The 
reading  of  vertical  angles  is  made  easier  by  the  arc  and 
vernier  being  graduated  on  their  edges. 

The  Beaman  Stadia  Arc  is  combined  with  the  edge 
graduated  vertical  arc  and  vernier,  thus  greatly  increas- 
ing the  usefulness  and  efficiency  of  the  instrument. 
This  patented  attachment,  as  described  on  pages  90  to 
96,  mechanically  reduces  stadia  readings  and  eliminates 
the  necessity  of  using  stadia  tables,  slide  rules  or  dia- 
grams. The  value  of  the  Beaman  Stadia  Arc  is 
evidenced  by  the  fact  that  this  attachment  is  regular 
equipment  on  all  Alidades  used  by  the  U.  S.  Geological 
Survey,  whose  engineers  are  the  largest  users  of  topo- 
graphic instruments  in  this  country.  Many  hundreds 
of  these  attachments  are  in  use  on  transits  and  telescopic 
alidades  and  are  giving  universal  satisfaction. 

Alidade  No.  584-C  is  standard  with  the  U.  S.  Geo- 
logical Survey,  which  is  using  large  numbers  of  Gurley 
Instruments  of  this  pattern.  Johnson  Plane  Table 
Outfit  No.  576-C,  as  illustrated  and  described  on  page 
244,  is  part  of  its  regular  equipment  and  has  been  de- 
veloped and  improved  by  co-operation  with  its  engineers. 


PLANE  TABLES  249 


GURLEY   EXPLORERS   ALIDADE 

No.  592-C  EXPLORERS  ALIDADE  is  of  special  interest 
to  topographers,  geographers,  geologists  and  landscape 
engineers  needing  a  serviceable,  dependable,  light  weight 
alidade. 

The  Explorers  Alidade  is  a  modification  of  the  well 
known  No.  584-C  Gurley  Alidade,  U.  S.  Geological 
Survey  standard.  It  is  smaller  and  lighter,  yet  built 
with  precisely  the  same  care  and  accuracy. 


FIG.  98 

No.  592-C  EXPLORERS  ALIDADE,  WITH  GRADIENTER  AND 
BEAMAN  STADIA  ARC 

The  majority  of  these  alidades  are  ordered  with  the 
Beaman  Stadia  Arc,  a  patented  device  controlled  by  us 
which  gives  accuracy  and  speed  to  stadia  surveying  that 
can  be  obtained  by  no  other  method.  See  pages  90  to  96. 

The  Gradienter  attachment  will  prove  useful  in  the 
measurement  of  distances  and  the  establishment  of 
grades.  The  Gradienter  head  and  index  are  graduated 


250         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

on  sterling  silver,  thus  the  graduations  are  clear,  distinct 
and  permanent.  The  entire  attachment  is  of  such  con- 
struction and  workmanship  that  it  can  be  depended  upon 
for  accurate  work.  See  pages  97  to  100. 

The  Explorers  Alidade  constitutes  an  appropriate 
companion  to  our  well  known  Explorers  Transit  and 
Explorers  Level,  and  the  three  instruments  can  be 
packed  conveniently  in  a  24  inch  dress  Suit  case. 

In  connection  with  our  special  light  weight  Johnson 
Plane  Table  Movement  No.  571,  and  either  the  15x15 
inch  or  the  18  x  24  inch  Drawing  Board,  it  provides  an 
outfit  for  topographical  surveying  which  cannot  be  ex- 
celled for  combined  accuracy  and  extreme  portability. 
The  Explorers  Alidade  can  also  be  used  successfully 
with  the  Traverse  Plane  Table. 

To  USE  THE  PLANE  TABLE 

To  obtain  the  best  results  with  the  plane  table  a 
certain  number  of  control  stations  should  first  be  located 
by  means  of  more  accurate  instruments,  such  as  a  transit 
and  spirit  level.  The  extent  of  this  control  will  depend 
on  the  requirements  of  the  survey  and  the  scale  of  the 
map.  The  plane  table  may  be  oriented  by  sighting  the 
previously  located  control  stations,  whose  positions  have 
been  carefully  plotted  on  the  drawing  paper.  With 
reasonable  care  any  direction  may  be  represented  in 
true  azimuth,  with  no  error  that  can  be  measured  on  the 
map  and  with  far  greater  accuracy  than  that  obtained 
by  plotting  angles  with  a  protractor.  The  plane  table 


PLANE  TABLES  251 


may  be  used  in  traverse  work  with  orientation  obtained 
by  compass  needle  or  solar  chart.  Or  a  direction  may 
be  assumed  and  a  traverse  executed  by  the  "fore  and 
backsight"  method  —  that  is,  by  drawing  a  long  line  for 
the  fore-sight  and  using  the  same  line  at  the  forward 
station  for  the  backsight.  In  other  words,  the  plane 
table,  though  it  can  not  be  used  for  determining  angular 
values  in  degrees,  minutes,  and  seconds,  is  capable  of 
measuring  all  horizontal  directions  that  can  be  measured 
by  a  transit  and  of  performing  these  functions  with 
errors  less  than  those  that  can  be  measured  on  the  map. 
The  accuracy  of  measurements  of  distances  by  tape 
depends,  of  course,  on  the  tape  and  not  on  the  plane 
table.  The  avoidance  of  errors  in  plotting  distances  by 
the  plane  table,  as  in  plotting  distances  from  transit 
notes,  depends  on  the  care  and  skill  of  the  surveyor. 
Under  average  conditions  the  errors  by  one  method  will 
be  no  greater  than  by  the  other. 

In  making  an  accurate  map  of  a  large  area  by  the 
plane  table,  two  or  more  control  points,  the  distances 
between  which  are  known,  must  be  given,  and  the  eleva- 
tion of  at  least  one  of  these  points  must  also  be  given. 
These  points  should  be  plotted  on  the  plane-table  paper 
in  their  proper  relative  positions.  If  the  scale  of  the 
map  is  too  small  to  justify  the  location  of  the  principal 
points  by  stadia,  they  may  be  accurately  located  by  inter- 
secting lines  drawn  from  two  or  more  stations.  Eleva- 
tions are  computed  from  vertical  angles,  the  distances 
being  scaled  from  the  plane-table  sheet.  After  a 
sufficient  number  of  points  have  been  located  the  con- 


252         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

tours  and  the  other  topographic  features  may  be  sketched 
on  the  sheet.  The  number  of  stations  that  should  be 
occupied  and  the  number  of  points  that  should  be  located 
to  produce  an  accurate  map  must  be  determined  by  the 
character  of  the  country  and  the  requirements  of  the 
scale  of  the  map. 

After  the  topographic  details  that  are  visible  from 
the  first  station  are  drawn  on  the  plane-table  paper  other 
stations  are  occupied,  where  the  same  operations  are 
performed  until  the  entire  area  is  covered.  This  com- 
pletes the  field  work,  and  the  only  additional  work  that 
may  be  required  is  that  of  inking  the  pencil  lines  if  the 
map  is  to  be  reproduced  by  photography.  The  inked 
map  is  used  by  the  Geological  Survey  as  the  final  copy 
for  the  engraver. 

If  a  plane-table  station  must  be  established  at  a  point 
not  previously  located,  its  exact  relative  position  on  the 
paper  can  be  found  in  a  few  minutes  by  the  well-known 
"three-point  method"  provided  three  or  more  previously 
located  points  are  visible. 

The  plane-table  method  may  be  recommended  for 
nearly  all  topographical  mapping.  In  high  latitudes, 
however,  where  outdoor  work  is  limited  to  two  or  three 
months  in  the  year  and  much  time  is  lost  by  storms,  even 
in  midsummer,  every  minute  spent  in  station  work  is  of 
great  value. 

Although  the  plane  table  is  generally  regarded  as 
the  instrument  best  fitted  for  topographic  mapping;  it 
is  also  useful  for  making  reconnaissance  or  preliminary 


PLANE  TABLES  253 


surveys  for  railways  and  highways,  for  locating  canals 
and  ditches,  for  mapping  civic  improvements  such  as 
parks  and  subdivisions  of  lots,  and  for  any  other  field 
surveys  in  which  it  is  not  necessary  to  determine  and 
record  angles  in  figures. 

Before  beginning  such  a  survey  with  the  plane  table 
the  accuracy  of  the  setting  of  the  stadia  wires  in  the 
telescope  of  the  alidade  should  be  tested  by  measuring 
off  a  horizontal  distance  of  about  1,000  feet,  comparing 
the  distance  as  measured  by  tape  and  stadia  for  each  100 
feet,  and  making  a  correction  table  for  the  stadia 
measurements  if  it  is  necessary. 

The  following  procedure  may  be  adopted  in  making 
a  reconnaissance  survey  with  the  plane  table: 

Set  up  the  plane  table  and  level  it  by  means  of  the 
circular  level  on  the  alidade.  The  board  need  not  be 
exactly  level,  though  it  is  more  convenient  to  have  its 
surface  very  nearly  so.  Test  the  adjustments  of  the 
alidade  and  correct  if  necessary.  Turn  the  board  till 
one  edge  is  parallel  with  a  north  and  south  line  as  indi- 
cated by  the  compass  attached  to  the  alidade.  This  line 
should  then  be  plainly  marked  on  the  paper  for  use  at 
subsequent  stations.  The  survey  is  then  carried  forward 
according  to  the  general  method  employed  when  a  transit 
is  used.  The  topographer  places  stakes  at  intervals  of 
100  feet  along  the  proposed  route  and  plots  them  at 
once  in  their  proper  positions  on  the  map  instead  of 
recording  bearings  and  distances  in  a  notebook  as  he 
does  when  he  uses  a  transit.  The  alidade  is  pointed 
toward  each  feature  that  is  to  be  located,  and  its  dis- 


254         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

tance  as  found  by  stadia  is  laid  off  in  the  direction  thus 
indicated.  The  elevation  is  found  from  vertical  angles 
or  by  direct  leveling.  From  each  plane-table  station 
the  topographer  locates  accurately  upon  the  sheet  the 
land  corners,  road  intersections,  and  other  conspicuous 
features  and,  with  the  area  in  plain  view,  draws  the 
contours.  He  then  carries  the  plane  table  forward  500 
or  1,000  feet  to  another  station  and  repeats  the  process. 
In  thick  timber  or  brush,  or  in  places  where  hills  inter- 
vene between  stations,  it  may  be  necessary  to  set  up  the 
plane  table  at  stations  off  the  line  in  order  to  cover  a 
wider  area  with  the  sketching  than  that  which  is  visible 
from  the  main  stations.  As  many  elevations  as  are  de- 
sired may  be  determined  and  recorded  on  the  map  in 
figures. 

Cross  sections  on  the  line  can  be  computed  by  the 
usual  methods,  but  careful  contouring  will  usually  give 
results  that  are  equally  valuable  for  computing  cuts  and 
fills.  For  preliminary  surveys  tape  measurements  can 
be  dispensed  with  and  stadia  distances  depended  on 
entirely.  The  methods  just  described  have  been  used 
for  railway  surveys.  Those  who  are  familiar  with  the 
plane  table  are  fully  convinced  that  a  map  made  by  its 
use  for  a  railway  or  for  a  similar  work  differs  in  no 
essential  feature  from  a  map  made  by  a  transit  survey, 
and  the  plane  table  has  the  advantage  of  affording 
greater  speed  and  of  obtaining  satisfactory  results  at 
less  cost. 

The  objection  has  been  made  that  the  scale  of  a 
plane-table  sheet  is  impaired  by  exposure  to  the  weather. 


PLANE  TABLES  255 


No  textbook  fails  to  call  attention  to  the  danger  of  such 
exposure,  so  that  many  have  been  led  to  believe  that  the 
scale  of  the  map  may  be  affected  in  this  way,  but  under 
ordinary  circumstances  no  serious  change  of  scale  occurs 
even  in  a  plane-table  sheet  that  has  been  exposed  to  the 
elements  for  a  long  time.  One  of  the  United  States 
Geological  Survey's  maps  that  was  recently  brought  in 
from  the  field  was  carefully  measured  with  the  same 
standard  scale  by  which  it  was  originally  constructed 
and  the  change  in  its  dimensions  was  found  to  be  of  no 
consequence.  The  measurements  showed  no  change  in 
its  width  at  top  or  bottom  and  a  change  of  only  one  one- 
hundredth  of  an  inch  throughout  its  length  of  22.8 
inches  —  a  change  so  trifling  as  to  be  negligible.  Other 
similar  tests  have  given  like  results. 

ADJUSTMENTS  OF  TELESCOPIC  ALIDADES 

There  are  three  field  adjustments  to  be  checked 
when  using  the  instruments. 

The  adjustment  of  the  striding  level, 

The  adjustment  of  the  line  of  collimation, 

The  adjustment  of  the  vernier  setting. 

The  last  adjustment  will  probably  not  be  necessary 
for  the  No.  584-C  Alidades. 

THE  STRIDING  LEVEL  is  adjusted  as  follows:  level 
up  the  telescope,  reverse  the  striding  level  end  for  end 
and  correct  half  of  the  apparent  error  by  means  of  the 
adjusting  screw  at  one  end  of  the  vial,  repeating  the 


256         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

operation  until  the  bubble  remains  in  the  center  of  the 
vial  for  both  positions  of  the  striding  level. 

LINE  OF  COLLIMATION.  Loosen  the  knurled  collar 
in  front  of  the  longitudinal  telescope  bearing.  Focusing 
the  telescope  on  a  distant  point,  revolve  the  telescope 
180°  in  its  collar  and  if  the  intersection  of  the  cross 
hairs  remains  on  the  distant  point  the  line  of  collimation 
is  in  the  optical  center  of  the  telescope.  If  this  con- 
dition does  not  obtain  correct  one  half  of  the  apparent 
error  by  means  of  the  capstan  head  nuts  on  the  exterior 
of  the  telescope  and  repeat  the  adjustment  operation. 

To  make  the  vertical  wire  truly  vertical,  level  the 
table  by  means  of  the  sensitive  striding  level  and  make 
the  vertical  wire  traverse  a  distant  point  when  the  tele- 
scope is  moved  on  its  horizontal  axis.  Correct  the  total 
apparent  error. 

To  ADJUST  THE  VERNIER.  Make  sure  that  the 
striding  level  and  the  line  of  collimation  are  in  perfect 
adjustment,  clamp  the  telescope  and  with  the  tangent 
screw  bring  the  level  bubble  to  the  center. 

When  the  bubble  is  in  the  center  of  the  level  the 
vernier  should  read  exactly  30°.  On  the  No.  592-C 
Alidades  the  vernier  can  be  brought  into  the  proper 
position  by  means  of  the  tangent  screw.  On  the  large 
No.  584-B  and  C  Alidades  it  would  be  necessary  to  move 
the  vernier.  This  can  be  accomplished  by  loosening  the 
two  screws  which  hold  the  vernier  in  place  and  moving 
it  slightly  to  get  the  proper  setting. 


PLANE  TABLES 


257 


GURLEY  TRAVERSE  PLANE  TABLE 

The  illustration  No.  586  represents  a  simple  form 
of  plane  table  and  alidade  first  made  by  us  for  the  U.  S. 
Geological  Survey,  and  in  its  present  improved  form 
is  used  extensively  for  traverse  work.  While  not  capable 
of  as  accurate  work  as  the  larger  plane  tables,  it  consti- 
tutes a  light  and  portable  instrument  for  topography. 


FIG.  99 
No.  586  TRAVERSE  PLANE  TABLE  OUTFIT 

The  board  can  be  equipped  with  the  extension  leg 
tripod  or  with  the  jointed  extension  leg  tripod. 

The  board  is  15  inches  square,  and  has  on  its  under 
side  a  strong  brass  flange  with  spring,  in  which  the 
plunger  clamp  of  the  tripod  head  engages,  allowing  the 


258 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


board  to  be  clamped  or  oriented  as  desired.  Small 
clamp  screws  with  sockets  for  holding  the  paper  are 
placed  at  the  corners  of  the  board.  Inserted  in  one 
edge  of  the  board  is  a  small  box  compass  with  needle, 
4>  inches  long. 


FIG.  100 

TRAVERSE  PLANE  TABLE  MOVEMENT,  SHOWING  THE  TRIPOD 

HEAD  AND  LEGS,  THE  PLUNGER  CLAMP  SCREW,  AND 

THE   IMPROVED   SPRING  BOARD   PLATE 


PLANE  TABLES  259 


The  alidade  consists  of  a  brass  ruler  10  inches  long, 
graduated  on  the  beveled  edge  to  a  scale  of  40  parts  to 
the  inch,  and  having  at  each  end*  hinged  sights  which 
fold  close  to  the  surface  of  the  ruler.  One  sight  has  a 
slit  and  the  other  a  hair.  The  alidade  is  furnished  with 
a  leather  pouch. 


FIG.  101 
No.   590-A   POCKET  SIGHT  ALIDADE, 

WITH    FOLDING    SIGHTS 

•\\ 

POCKET  SIGHT  ALIDADE  No.  590-A  is  6"  long  and 
has  hinged  sights  which  fold  down  flat  on  the  ruler.  *j 

The  beveled  edge  is  graduated  the  entire  length  to 
read  1/10  and  1/20  of  a  mile  for  ratios  of  1/90,000 
and  1/45,000  .respectively.  The  middle  part  of  the 
edge  is  further  divided  to  read  1/50  and  1/100  of  a 
mile  respectively  for  the  same  two  ratios. 

This  alidade  is  furnished  with  leather  case  having 
pencil  pockets. 


260         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

ARMY   SKETCHING   CASE 

THIS  instrument  for  topographic  map  making  was 
originally  designed  especially  for  the  use  of  U.  S. 
Army  Engineers,  but  since  its  introduction  has  been 
found  unusually  serviceable  for  a  similar  class  of  work 
by  foresters,  geologists,  road  engineers,  timber  cruisers 
and  civil  engineers. 

Several  hundreds  of  these  efficient  field  sketching 
outfits  are  being  used  successfully  by  officers  and  men 
in  practically  every  branch  of  the  Army  and  by  the 
various  Army  Service  Schools;  also  by  military  acad- 
emies, militia  organizations,  civil  engineers  and  sur- 
veyors. 

In  addition  to  the  simplicity  and  strength  of  con- 
struction fitting  it  for  general  use,  this  sketching  case 
possesses  a  unique  feature  in  that  the  board  does  not 
require  to  be  oriented  in  taking  observations.  So  far  as 
we  know,  this  is  the  only  practical  sketching  case  on  the 
market  having  this  valuable  feature,  which  makes  its 
operation  very  simple  and  rapid.  The  use  of  a  tripod 
is  unnecessary  and  there  is  no  complicated  protractor  to 
operate.  In  fact,  anyone  can  readily  learn  to  use  this 
instrument  after  studying  the  directions  carefully. 

CONSTRUCTION 

,  The  Army  Sketching  Case  consists  of  a  plane  table 
board,  six  inches  by  twelve  inches,  made  of  seasoned 
pine  with  mahogany  end  pieces.  This  construction  in- 
sures a  strong,  durable  board  which  will  not  warp  nor 


PLANE  TABLES 


261 


pull  apart  under  hard  service.  To  the  lower  right  hand 
side  is  attached  a  compass  box  with  floating  dial,  three 
inches  in  diameter,  beveled  on  the  edge  and  graduated 
into  360  degrees. 

A  protected  opening  in  the  compass  box  permits  the 
graduated  dial  to  be  read  either  from  above  or  when  the 
board  is  held  level  with  the  eye  of  the  observer. 


I 


FIG.  102 

No.  594  ARMY  SKETCHING  CASE 
PATENTED  SEPT.  1,  1908 

Designed  by  Lt.  Col.  Glenn  S.  Smith  of  the 
U.  S.  Geological  Survey 


262         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Rifle  sights  which  are  placed  in  line  with  the  center 
of  the  compass  and  parallel  with  the  edge  of  the  board, 
are  used  as  an  alidade  in  taking  bearings. 

On  the  upper  side  of  the  board  is  mounted  a  circular 
plate,  six  inches  in  diameter,  and  pivoted  at  the  center. 
This  plate  is  attached  to  an  L-shaped  base  at  the  upper 
end  of  which  is  a  cylinder  through  which  passes  a  rod 
parallel  with  and  secured  to  the  top  of  the  board. 

A  metal  strip  let  into  a  slot  in  the  middle  of  the 
board  guides  the  lower  edge  of  the  L-shaped  base. 

Upon  the  guides  as  described,  the  base  carrying  the 
circular  plate  can  be  moved  from  side  to  side  over  the 
upper  surface  of  the  board  and  clamped  at  will  by  a 
set  screw  in  the  cylinder  at  the  top. 

A  clamp  with  index  line  is  so  attached  to  the  base 
that  the  circular  plate  mounted  upon  it  may  be  set  at 
any  desired  position. 

A  card  of  aluminum  is  attached  to  the  circular  plate 
and  upon  this  card  a  combined  protractor  and  scale  are 
printed. 

The  protractor  is  graduated  into  360  degrees  and 
the  scale  consists  of  a  series  of  equally  spaced  concen- 
tric circles. 

Different  protractor  cards  are  furnished  for  the 
various  scales  used  in  map  making. 

Rollers  with  friction  brakes,  attached  to  two  edges 
of  the  board,  receive  the  paper  and  hold  it  snugly  against 
the  surface  of  the  protractor  which  travels  underneath 


PLANE  TABLES  263 


it.     An  aluminum  shield  protects  the   paper   and  pre- 
vents soiling. 

To  the  under  side  of  the  board  a  swiveling  strap, 
with  buckle,  is  attached,  by  means  of  which  the  case  can 
be  firmly  secured  to  the  observers  arm.  There  is  also 
a  socket  by  which  a  tripod  or  staff  may  be  attached.  A 
simple  clinometer  attachment  for  taking  slopes  is  also 
provided. 

As  far  as  possible  the  metal  parts  are  made  of  alum- 
inum, so  that  the  case  weighs  only  about  two  pounds, 
and  they  are  of  dark  finish  to  avoid  reflection  of  sun- 
light. 

Care  in  the  selection  of  a  proper  material  for  use 
On  the  case  in  recording  observations  is  essential  to 
successful  operation,  and  tracing  cloth  should  be  avoided 
as  too  smooth  for  the  use  of  a  pencil.  Vellum  tracing 
paper  has  a  slightly  roughened  surface,  little  affected 
by  moisture  and  on  which  the  pencil  works  well,  is 
recommended. 

On  completion  of  the  survey,  the  sketch  may  be  taken 
from  the  instrument  and  blue  prints  made  directly  from 
the  original. 

Detailed  directions  for  using  the  Army  Sketching 
Case  are  furnished  with  each  instrument.  A  descriptive 
circular  containing  these  instructions  will  be  sent  free 
to  any  address  on  request. 


264         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

FIALA  SCOUT  SKETCHING  CASE 

The  interest  in  map  sketching  as  practiced  by  army 
engineers  is  increasing,  and  the  necessity  for  a  more 
general  knowledge  along  these  lines  is  evidenced  by  the 
taking  up  of  such  work  by  various  organizations  of  the 
National  Guard. 


FIG.  103 
SHOWING  METHOD  OF  USING  FIALA  SCOUT  SKETCHING  CASE 

For  convenience  in  making  maps  in  the  field  various 
forms  of  sketching  cases  are  used,  consisting  of  a  small 
drawing  board  provided  with  a  magnetic  compass,  ali- 


PLANE  TABLES  265 


dade  (or  scale)  with  sights,  and  rollers  for  carrying  a 
supply  of  paper.  Sketches  are  made  with  colored 
pencils. 

With  such  equipment,  topographical  maps  can  he 
accurately  and  rapidly  made  to  show  the  character  of 
the  land,  whether  level  or  mountainous,  fertile  or  barren ; 
the  location  of  railroads,  highways,  water  courses,  and 
bridges  or  structures  of  any  kind. 

Map  making  is  a  very  necessary  part  of  a  Boy 
Scout's  course  in  surveying.  By  means  of  a  sketching 
case  he  can  make  a  record  of  the  country  traversed  on 
his  "hikes,"  and  thus  develop  his  sense  of  proportion, 
direction  and  distance  in  an  instructive  and  interesting 
manner.  Canoeists  and  campers  also  can  use  a  device 
of  this  kind  to  advantage. 

The  Fiala  Scout  Sketching  Case  is  a  practical  instru- 
ment in  every  particular.  It  was  designed  and  made 
from  suggestions  by  Mr.  Anthony  Fiala,  the  explorer, 
whose  experience  in  the  Arctic  regions  and  with  Colonel 
Roosevelt  in  South  America  places  him  in  a  position  to 
fully  understand  the  needs  of  those  engaged  in  outdoor 
pursuits. 


266         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Designed  along  the  same  general  lines  as  the  Army 
professional  model,,  No.  594,  which  we  have  made  for  a 
number  of  years  for  military  topographers  and  others, 
the  Fiala  case  is  much  less  elaborate  and  expensive  but 
is  efficient  and  convenient  as  well  as  of  value  for  educa- 
tional purposes. 


FIG.  104 
No.  596  FIALA  SCOUT  SKETCHING  CASE 

The  Fiala  Scout  Sketching  Case  consists  of  a 
thoroughly  seasoned  white  pine  drawing  board,  6  inches 
wide  x  5  inches  long,  having  %  inch  diameter  rollers 
at  each  end  which  carry  a  strip  of  white,  strong,  smooth- 
faced architects  paper,  5%  x  36  inches.  An  adjustable 
device  on  the  rollers  holds  the  paper  flat  against  the 
board  and  prevents  it  from  uncoiling.  Fitted  into  the 
right  hand  end  of  the  board  is  a  brass  compass  having 


PLANE  TABLES  267 


a  1%  inch  needle  with  needle  stop  and  slotted  revolving 
cover.  Holes  bored  into  the  left  hand  end  of  the  board 
contain  three  sketching  pencils,  black,  red  and  blue. 
These  are  held  securely  by  means  of  a  brass  spring  clip. 

A  boxwood  ruler,  6  inches  long,  with  small  brass 
folding  sights  at  each  end,  enables  the  user  to  establish 
the  bearings  of  lines.  The  ruler  has  scale  of  6  inches 
to  1  mile  on  one  edge,  and  3  inches  to  1  mile  on  the 
other.  Two  rubber  bands  are  used  to  aid  in  holding  the 
ruler  on  the  paper.  The  ruler  is  fastened  to  one  of  the 
roller  knobs  by  a  cord  and  when  not  in  use  is  securely 
held  against  the  back  of  the  board  by  a  brass  spring  clip. 

There  is  a  simple  form  of  clinometer  for  determining 
angles  of  slope.  The  ruler  alidade  is  arranged  to  swing 
across  the  surface  of  the  paper  and  the  angles  of  slope 
are  read  on  a  scale  attached  to  the  left  hand  edge  of 
the  case. 

In  use,  the  sketching  case  is  fastened  to  the  forearm 
of  the  sketcher  by  a  leather  strap  on  the  back  of  the 
board.  It  weighs  about  30  ounces  and  measures 
9  x  7%  x  1  inch.  Packed  for  parcel  post  shipment,  it 
weighs  3  pounds.  Architects  Drawing  Paper,  in  rolls 
5%  x  36  inches,  per  roll,  is  furnished  for  use  with 
this  case. 


268         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

CHAINS   AND   TAPES 

The  Surveyors  and  Engineers  Chains  are  the  measur- 
ing instruments  by  which  our  oldest  surveys  were  made 
and  many  farm  surveys  are  made. 

We  furnish  tapes  of  all  standard  units  and  lengths 
in  Nos.  8  and  10  refined  iron  wire  and  in  Nos.  8,  10 
and  12  best  steel  wire.  Steel  chains  are  preferred  on 
account  of  their  greater  strength,  although  they  are 
more  expensive  than  those  of  iron. 

BRAZED  STEEL  CHAINS.  A  very  light  and  strong 
chain  is  made  of  No.  12  steel,  securely  brazed.  The 
wire  is  of  a  low  spring  temper,  and  the  chain,  though 
light,  is  almost  incapable  of  being  broken  or  stretched 
in  careful  use. 

METER  AND  VARA  CHAINS.  The  meter  is  used  as  a 
standard  measure  of  length  in  many  countries,  and 
chains  of  ten  and  twenty  meters  are  often  ordered.  The 
chains  are  of  Nos.  10  and  12  iron  or  steel  wire,  each 
meter  being  divided  into  five  links.  The  old  surveys 
of  Texas  were  made  with  the  vara  as  the  unit  of 
measure  and  we  supply  Vara  Chains  of  Nos.  8,  10  and 
12  iron  or  steel  wire. 

CHAIN  TAPES 

Chain  tapes  are  generally  used  on  bridge,  road  and 
street  work,  and  as  standards  for  comparison  of  other 
chains  and  tapes.  They  are  made  of  a  thin  ribbon  of 
steel  about  one  quarter  of  an  inch  wide,  and  of  straight 


CHAINS  AND  TAPES  269 

spring  temper,  and  in  lengths  of  from  sixty-six  to  five 
hundred  feet. 

STEEL  RIBBON  CHAIN  TAPES 

One-quarter  inch  wide,  heavy  steel  ribbon,  deeply 
etched  graduations,  large  detachable  handles  and  a 
wooden  reel  with  nickel  trimmings. 

The  sixty-six  and  one  hundred  thirty-two  feet 
lengths  are  usually  graduated  at  each  Gunter's  link  for 
use  in  land  surveying,  and  the  one  hundred  to  five  hun- 
dred feet  lengths  are  graduated  at  each  foot,  with  the 
first  and  last  foot  marked  in  tenths,  for  city  work. 

METALLIC  TAPES 

These  are  of  linen,  about  five  eighths  of  an  inch 
wide,  and  have  fine  brass  wires  interwoven  through  their 
whole  length.  They  are  thus  measurably  correct,  even 
when  wet. 

They  are  graduated  in  feet  and  tenths  or  in  feet  and 
inches,  on  one  side,  as  ordered,  and  are  marked  in  links 
on  the  reverse  side.  They  are  wound  in  a  leather  case 
having  a  folding  handle. 

STEEL  TAPES 

The  best  tapes  are  made  of  a  thin  ribbon  of  steel  in 
one  piece,  of  straight  spring  temper,  and  either  one 
quarter,  three  eighths  or  one  half  inch  wide. 

They  are  made  in  all  lengths  from  twenty-five  to 
two  hundred  feet,  graduated  to  feet,  inches,  and  eighths 


270         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

of  an  inch,  or  more  usually  feet,  tenths  and  hundredths 
of  a  foot. 

They  are  also  graduated  at  each  Gunter's  link,  on 
the  reverse  side  if  desired.  The  figures  and  graduations 
are  etched  on  the  surface  of  the  steel. 

The  Engineers  Pattern  steel  tapes  are  made  of  thin 
steel  ribbon,  about  one  quarter  of  an  inch  wide  and  of 
straight  spring  temper.  They  can  be  detached  from  the 
case  when  desired,  and  used  with  a  pair  of  handles  for 
chain  measurements.  They  can  also  be  used  with 
handles  having  a  compensation  scale  for  variations  of 
temperature. 

These  tapes  are  U.  S.  standard  measure  at  62° 
Fahrenheit,  with  about  twelve  pounds  strain.  A  hun- 
dred foot  tape  expands  .0756  inch  for  each  10°  rise  in 
temperature. 

The  tapes  are  wound  in  a  leather  or  metal  case  with 
folding  handle. 

Our  steel  tapes  Nos.  850  to  854-B  are  very  popular 
for  underground  work.  They  are  one  half  inch  wide, 
and  are  mounted  on  an  open  brass  frame,  nickel  plated, 
and  with  double  folding  flush  handle.  They  are  easily 
wound  and  unwound,  and  the  open  frame  allows  the 
evaporation  of  moisture.  This  feature  is  also  character- 
istic of  the  reels  supplied  on  our  Wolverine  Tapes  Nos. 
814  to  817. 


CHAINS  AND  TAPES  271 

METRIC  AND  VARA  TAPES 

We  can  furnish  any  of  our  metallic  tapes,  and  steel 
tapes,  with  metric  or  vara  measure  on  the  reverse  side 
instead  of  links.  Tapes  of  metric  or  vara  measure  only 
can  also  be  supplied. 

Our  extra  heavy  metric  chain  tapes,  Nos.  M20  to 
Ml 00,  are  graduated  with  metric  measure  only,  and  are 
marked  in  decimeters,  with  the  first  meter  in  centimeters 
and  the  first  decimeter  in  millimeters.  If  graduated 
with  vara  measure  only,  they  are  marked  in  tenths  of 
a  vara. 

MARKING  PINS 

In  chaining,  eleven  marking  pins  are  needed,  made 
either  of  iron,  steel  or  brass  wire,  as  preferred.  They 
are  about  fourteen  inches  long,  pointed  at  one  end  to 
enter  the  ground,  and  formed  into  a  ring  at  the  other 
end  for  convenience  in  handling. 

Marking  pins  are  sometimes  loaded  with  a  little 
mass  of  lead  around  the  lower  end,  to  serve  as  a  plumb 
when  the  pin  is  dropped  to  the  ground  from  the  sus- 
pended end  of  the  chain. 


272         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

PLUMMETS 

We  manufacture  plain  brass  plummets  like  that 
illustrated  in  Fig.  105  in  the  following  sizes:  6  oz.,  10 
oz.,  16  oz.,  24  oz.,  and  32  oz. 

If  the  work  at  hand  requires  a  long  plummet  of  small 
diameter  No.  460  twelve  ounce  plummet  is  supplied. 


FIG.  105 
Nos.  450  TO  458  PLAIN  PLUMMETS 


PLUMMETS 


273 


ADJUSTABLE  BRASS  PLUMMET  No.  465  has  a  con- 
cealed reel  R,  Fig.  106,  around  which  the  string  is 
wound  by  turning  the  milled  head  on  top.  The  friction 
upon  the  reel  will  hold  the  plummet  at  any  desired  point 
of  the  line. 


K 


FIG.  106 
No.  465  ADJUSTABLE   PLUMMET 

SHOWING   DETAILS    OF    CONCEALED    REEL 


274         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

HYDRAULIC 
ENGINEERING   INSTRUMENTS 

THE   importance  of  an  exact  knowledge  concerning 
the  surface  water  supply  of  the  country  has  been 
recognized  for  many  years.     The  immediate  neces- 
sity of  stream  flow  data,  to  be  used  by  those  interested 
in  or  engaged  upon  problems  of  hydraulic  engineering,, 
including  water  power,   domestic   water   supply,  inland 
navigation,  irrigation,  swamp  and  overflow  land  drainage 
and  flood  prevention,  has  created  a  constantly  increasing 
demand  for  a  means  of  obtaining  such  data  accurately. 

The  data  required  is  the  area  of  cross-section,  the 
velocity  of  flow  and  the  elevation  of  the  water,  with 
which  the  quantity  or  volume  of  flow  can  be  readily 
computed. 

The  area  of  cross-section  is  obtained  by  the  usual 
methods  of  surveying. 

Velocity  is  measured  by  Current  Meter  Measure- 
ments. 

The  varying  height  of  the  water  level  is  automati- 
cally recorded  by  Water  Stage  Register. 


HYDRAULIC  ENGINEERING  INSTRUMENTS          275 


CURRENT  METERS 

FOR  more  than  thirty  years  W.  &  L.  E.  Gurley  have 
made  Current  Meters  under  the  patents  of  W.  G. 
Price,    the    Assistant    Engineer    of    the    Corps    of 
Engineers,  United  States  Army,  who  in  1885  devised  the 
initial   pattern.     The   general   features   are   retained   in 
the  latest  models,  although   somewhat  modified   as   the 
result  of  suggestions  from  many  hydraulic  engineers  who 
have  had  large  experience  in  current  meter  observation 
under  all  conditions  of  service. 

The  many  hundreds  of  Gurley  Current  Meters  in 
use  in  all  parts  of  the  world,  their  constantly  increasing 
sale  and  their  accuracy  and  reliability  under  all  con- 
ditions, show  that  they  are  the  standard  instruments  for 
the  accurate  measurement  of  the  velocity  of  water  in 
streams  and  open  conduits. 

A  current  meter  for  measuring  the  velocity  of  flowing 
water  comprises  two  essential  parts:  (a)  a  wheel  ar- 
ranged so  that  when  suspended  in  flowing  water  the 
pressure  of  the  water  against  it  causes  it  to  revolve; 
(b)  a  device  for  recording  or  indicating  the  number  of 
revolutions  of  this  wheel.  The  relation  between  the 
velocity  of  the  moving  water  and  the  revolutions  of  the 
wheel  is  determined  by  rating  each  meter. 

The  distinguishing  characteristics  of  a  good  current 
meter  are  (a)  simplicity  in  construction,  with  no  delicate 
parts  which  easily  get  out  of  order;  (b)  a  small  area  of 
resistance  to  the  velocity  of  the  water;  (c)  a  simple 


276         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

and  effective  device  for  indicating  the  number  of  revolu- 
tions of  the  wheel;  and  (d)  easy  adaptability  to  use 
under  all  conditions. 

SELECTING  THE  PROPER  TYPE  OF  CURRENT  METER 

The  experience  of  many  years  has  shown  that  but 
two  patterns  of  the  Gurley  meter  are  needed  to  ade- 
quately meet  the  requirements  of  practically  all  engineers 
engaged  in  measuring  the  flow  of  water.  Accordingly, 
we  have  discontinued  making  the  large  pattern  formerly 
listed  as  Meter  No.  600,  and  also  two  of  the  smaller 
patterns,  previously  listed  in  different  combinations  as 
Meters  Nos.  617,  618,  621  and  624. 

We  will  continue  to  make  only  the  two  standard 
models,  namely  Accoustic  Meter  No.  616,  and  Electric 
Meter  No.  623.  The  latter  may  be  supplied  with  such 
a  variety  of  equipment  that  it  will  be  the  equivalent 
of,  and  can  be  used  for  the  same  work  as,  the  discon- 
tinued Meters  Nos.  617,  618,  621  and  624. 

The  selection  of  a  meter  should  be  made  after  con- 
sideration has  been  given  to  the  following  factors: 

(1)  The  purpose   for   which   the  instrument  is 

to  be  used. 

(2)  The  manner  in  which  it  is  supported. 

(3)  The  amount  of  weight  to  be  used. 

(4)  The   frequency   of   the     revolutions     to    be 

indicated. 


HYDRAULIC  ENGINEERING  INSTRUMENTS          277 


CURRENT  METER  No.  616.  When  it  is  possible  for 
the  observer  to  approach  the  stream  closely,  and  to  hold 
the  meter  in  position  by  means  of  its  suspension  rod, 


FIG.  107 
No.    616   ACOUSTIC    CURRENT   METER   OUTFIT 

WITH    JOINTED    WADING    RODS,    RUBBER    TUBE,    EAR 

PIECE    AND    CONNECTION,    INDICATING    EACH 

TENTH    REVOLUTION 

especially  in  channels  of  small  depth,  the  Acoustic  Cur- 
rent Meter,  No.  616,  is  very  useful. 


278         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

This  meter  indicates  every  tenth  revolution  of  the 
bucket  wheel  by  the  sound  of  a  hammer  striking  against 
a  diaphragm,  one  blow  for  every  10  revolutions.  The 
indicating  mechanism  is  completely  enclosed  and 
thoroughly  protected  from  injury.  When  in  use  the 
meter  is  held  by  a  jointed  wading  rod,  which  screws 
into  the  frame  and  in  connection  with  a  rubber  tube 
and  ear  piece  attached  to  it,  forms  a  passage  through 
which  the  sound  of  the  hammer  stroke  is  transmitted 
to  the  ear  of  the  observer.  This  enables  him  to  count 
the  number  of  revolutions  of  the  wheel  in  any  given 
space  of  time,  and  they  by  means  of  the  rating  table  to 
ascertain  the  velocity  of  flow. 

THE  ELECTRIC  INDICATOR.  Many  observers  prefer 
an  electric  type  of  revolution  indicator.  This  indi- 
cating device  is  protected  from  injury  by  enclosure  in 
the  contact  chambers,  or  commutation  boxes,  and  the 
revolutions  of  the  bucket  wheel  are  indicated  by  a  tele- 
phone ear  piece,  which  is  generally  fastened  in  a  con- 
venient position  on  the  observer's  coat. 

CURRENT  METER  No.  623  combines  all  of  the  advan- 
tages of  all  other  meters  previously  listed.  It  can  be 
suspended  by  cable  or  by  jointed  wading  rod,  and  is 
equipped  with  two  interchangeable  commutator  boxes 
for  indicating  each  revolution,  or  each  fifth  revolution, 
of  the  bucket  wheel. 

The  combination  of  these  features  provides  an  outfit 
which  has  been  adopted  as  standard  by  the  most  efficient 
hydraulic  engineers.  This  meter  is  used  extensively 


HYDRAULIC  ENGINEERING  INSTRUMENTS 


279 


by  the  Water  Resources  Branch  of  the  United  States 
Geological  Survey,  the  leading  organization  devoted  to 
the  precise  measurement  of  water. 

Two  contact  chambers,  one  to  indicate  each  revolu- 
tion, the  other  each  fifth  revolution  of  the  bucket  wheel, 


FIG.  108 
No.  623  ELECTRIC  CURRENT  METER  OUTFIT 

WITH    METER    SUSPENDED    BY    JOINTED    WADING    RODS 

are  provided.  These  contact  chambers  may  be  readily 
interchanged,  the  only  change  being  in  the  shaft  and 
consisting  of  the  insertion  of  a  cam  on  the  end  of  the 


280 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


bucket  shaft  when  a  single  revolution  is  to  be  indicated, 
or  the  insertion  of  a  worm  when  it  is  desired  to  indicate 
every  fifth  revolution. 

A  more  complete  description  of  current  meters  and 
their  parts,  as  well  as  water  stage  registers,  is  given  in 


FIG.  109 
No.  623  ELECTRIC  CURRENT  METER  OUTFIT 

WITH    METER    SUSPENDED    BY    CABLE 

"A  Manual  of  Gurley  Hydraulic  Engineering  Instru- 
ments", which  will  be  sent  upon  request.  The  Manual, 
besides  describing  the  meters,  gives  the  calibration 
charts  for  the  various  types  and  full  instructions  regard- 
ing the  use  of  hydraulic  instruments  in  general. 


HYDRAULIC  ENGINEERING  INSTRUMENTS          281 

ELECTRIC   REGISTER 

WHENEVER  it  is  desirable  to  record  the  revolu- 
tions of  the  bucket  wheel  of  Meters   Nos.  617, 
621  and  623,  an  Electric  Register  may  be  substi- 
tuted for  the  telephone  ear  piece  ordinarily  used. 

Electric  Register  No.  609  has  been  developed  recently 
by  us  and  is  a  great  improvement  over  the  former  pat- 
tern. It  is  suitable  for  use  with  current  meters  or  any 


FIG.  110 
No.  609  ELECTRIC  REGISTER 

other  intermittent  contact  device  of  which  a  record  is 
desired. 

This    device    consists    of    a    three    figure    "Veeder" 
counter  operated  by  an  electro-magnet  and  springs,  and 


282         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

is  so  arranged  that  the  same  force  acts  on  the  counter 
regardless  of  how  much  current  is  used.  This  results 
in  a  uniform  action  and  guarantees  against  any  skipping 
or  missing,  under  widely  varying  conditions. 

This  instrument  will  operate  under  favorable  condi- 
tions with  one  good  dry  cell,  but  should  have  two,  as  a 
protection  against  deterioration  of  the  battery.  It 
requires  but  0.31  ampere  with  two  cells,  which  is  a  much 
smaller  current  than  was  necessary  with  the  old  style 
register,  and  which  will  not  burn  the  current  meter 
contacts. 

There  are  no  dials  to  read,  the  total  result  being 
shown  directly  by  the  figures,  so  that  there  is  small 
chance  of  an  error  in  reading. 


HYDRAULIC  ENGINEERING  INSTRUMENTS 


283 


FIG.   Ill 

No.  628 

HOOK  GAGE 


HOOK  GAGE 

THIS  new  type  of  Hook  Gage 
was  designed  in  accordance 
with  suggestions  made  by 
Messrs.  Metcalf  and  Eddy,  Con- 
sulting Hydraulic  Engineers,  of 
Boston,  Mass.,  and  is  a  great 
improvement  over  other  patterns. 
Its  entire  arrangement  is  such  that 
the  readings  can  be  taken  by  the 
observer  with  the  greatest  possible 
convenience  and  at  some  distance 
from  the  surface  of  the  stream  or 
ditch  being  measured.  This  is  often 
a  decided  advantage,  especially  so 
in  the  East,  where  many  of  the 
streams  are  contaminated  by  dye 
stuffs  and  other  undesirable  ma- 
terial, rendering  it  unpleasant  for 
the  observer  to  get  too  close  to  the 
water. 

The  Hook  Gage  is  nickel-plated 
throughout.  The  tube  is  regularly 
made  to  read  to  2.2  feet  but  may  be 
made  longer  if  desired.  It  is  grad- 
uated to  feet,  tenths  and  hundredths, 
and  is  read  to  thousandths  by  a  ver- 
nier which  is  capable  of  fine  adjust- 
ment by  means  of  a  slow  motion 
screw.  Elongated  holes  in  the  base 
furnish  means  for  bolting  the  gage 


284.         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

to  the  side  of  the  flume.  The  hook  is  adjustable  within 
the  tube  and  allows  for  a  movement  of  12  inches  inde- 
pendent of  the  gage,  thus  permitting  it  to  be  set  accur- 
ately to  the  exact  surface  of  the  water. 

USE  OF  THE  HOOK  GAGE 

The  hook  gage  is  used  in  a  box  attached  to  a  flume 
at  any  convenient  point  near  the  weir,  the  water  from 
the  flume  being  conveyed  to  the  box  by  rubber  or  lead 
pipes,  thus  indicating  the  precise  level  of  the  water  in 
the  flume,  the  surface  of  the  water  in  the  box  being 
at  rest. 

When  the  depth  of  the  water  passing  over  a  weir  is 
required,  the  exact  level  of  the  crest  of  the  weir  should 
be  taken  by  a  leveling  instrument  and  rod,  and  marked 
by  a  line  drawn  in  the  still  water  box  at  the  surface  of 
the  water.  The  scale  of  the  gage  being  previously  set 
at  zero  with  the  vernier,  the  base  is  fastened  to  the  box 
above  the  water  in  a  vertical  position  and  at  such  a 
height  that  the  point  of  the  hook  is  at  the  same  level  as 
the  crest  of  the  weir,  the  precise  point  being  secured  by 
moving  the  hook  in  the  tube.  The  point  of  the  hook  will 
of  course  be  under  water  and  level  with  the  crest  of 
the  weir. 

The  depth  of  water  flowing  over  the  weir  is  the  dis- 
tance between  the  point  of  the  hook  in  the  position  named 
and  the  exact  surface  of  the  water.  To  ascertain  this, 
the  hook  is  raised  by  turning  the  milled  head  nut  until 
the  point  of  the  hook,  appearing  a  little  above  the  sur- 


HYDRAULIC  ENGINEERING  INSTRUMENTS          285 

face,  causes  a  distortion  in  the  reflection  of  the  light 
from  the  surface  of  the  water.  A  slight  movement  of 
the  hook  in  the  opposite  direction  will  cause  the  distor- 
tion to  disappear,  and  will  indicate  the  surface  with 
precision.  The  reading  of  the  scale  will  then  give  the 
depth  of  water  passing  over  the  weir,  in  thousandths 
of  a  foot. 

It  will  be  understood  from  the  illustration  that  the 
longer  movements  of  the  scale  are  made  by  loosening 
the  large  clamp  screw  and  sliding  the  graduated  tube 
through  the  frame,  the  finer  adjustments  being  made  by 
the  milled  nut. 


286         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


WATER  STAGE  REGISTERS 

THE   growing  importance   of   water   power  develop- 
ment, the  great  possibilities  for  its  use  in  irrigation 
and  the  many  other  ways  in  which  this  great  gift  of 
nature  may  be   employed  in  the   service  of  man,  have 
made   more  essential,   as   in  recent  years  its   value  has 
been  better  appreciated,  the  accurate  determination  of 
the  volume  of  water  in  streams  available  for  such  use. 

The  energy  of  some  of  the  foremost  engineers  in 
the  world  has  been  enlisted  in  the  work,  and  both 
methods  and  appliances  have  been  perfected  as  the 
result  of  experience. 

For  many  years  Gurley  Current  Meters  have  been 
in  use  in  all  parts  of  the  world  and  are  considered  stand- 
ard in  determining  the  velocity  of  the  flow  of  water  in 
streams. 

The  discharge  of  a  stream  is  usually  ascertained  by 
a  comparison  of  gage  heights  with  a  rating  table  of 
the  discharge  of  the  stream  at  varying  heights,  com- 
piled from  a  series  of  current  meter  observations. 

The  greatest  error  in  these  estimates  is  due  to  inac- 
curate determination  of  the  gage  heights,  ordinarily 
secured  from  a  few  observations  taken  during  the  day, 
or  even  more  infrequently. 

It  has  been  found  that  on  many  streams  there  is  a 
considerable  daily  fluctuation  due  to  natural  or  artificial 
control,  making  it  impossible  to  obtain  accurate  gage 


HYDRAULIC  ENGINEERING  INSTRUMENTS          287 

heights  without  the  use  of  an  automatic  register  which 
will  record  the  height  of  water  at  regular  intervals  dur- 
ing the  entire  twenty-four  hours,  or  over  a  longer  period 
of  time. 

In  the  endeavor  to  produce  instruments  satisfactory 
for  such  purposes,  we  have  for  several  years  been  en- 
gaged in  designing  Water  Stage  Registers  by  which  the 
varying  height  of  water  in  streams  may  be  gaged  and  a 
dependable  continuous  record  be  obtained. 

As  a  result  of  our  efforts,  coupled  with  the  sugges- 
tions made  by  eminent  engineers,  familiar  with  the 
problems  involved,  we  have  produced  several  patterns 
of  Water  Stage  Registers  which  are  satisfactorily  meet- 
ing the  demands  of  the  service  for  reliable  instruments 
giving  accurate  and  uniform  records. 

Automatic  Water  Stage  Registers  are  divided  into 
two  classes  —  those  making  a  printed  record,  and  those 
making  a  graphic  record.  In  the  first  type  a  printed 
record  of  the  height  and  time  is  made,  while  in  the 
second  type  the  record  is  traced  by  a  pen  or  pencil  on 
the  surface  of  a  paper  sheet,  moving  in  harmony  with 
the  time  and  height. 

The  first  type  of  register  is  designed  to  give  printed 
records  of  the  rise  and  fall  of  water  continuously  for  a 
long  period  of  time,  and  is  especially  adapted  for  places 
where  it  is  impractical  or  impossible,  by  reason  of 
inaccessibility,  for  the  observer  to  visit  the  station  for 
long  intervals  of  time  and  where  the  record,  to  be  of 
service,  should  be  continuous. 


288         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

No.  630  PRINTING  WATER  STAGE  REGISTER 
Patented  January   10,,   1911 

The  difficulty  of  scaling  with  precision  the  records 
made  by  a  graphic  register,  the  tendency  of  the  paper 
to  be  affected  by  moisture  or  other  causes,  and  the  lim- 
ited time  for  which  the  record  can  be  taken,  have  led  to 
our  introducing  a  register  which  prints  on  a  continuous 
paper  strip,  at  intervals  of  15  minutes,  the  height  of  the 
water  in  feet  and  hundredths  of  a  foot  for  a  period  of 
time  dependent  on  the  range  of  fall  allowed  the  driving 
weights,  which  move  at  the  rate  of  one  and  one  half 
inches  during  a  period  of  24  hours. 

This  register  is  the  result  of  years  of  study  and 
experiment,  and  is  made  in  the  best  manner  and  of  the 
best  material.  It  has  had  the  original  inspection  and  ap- 
proval of  some  of  the  most  eminent  hydraulic  engineers, 
and  has  been  tested  under  severe  conditions  of  actual 
service  with  most  satisfactory  results.  We,  therefore, 
have  no  hesitation  in  recommending  its  use  to  all  who 
require  accuracy  and  efficiency  in  water  measurements. 

CONSTRUCTION.  By  reference  to  the  illustrations,  a 
clear  idea  can  be  gained  of  the  mechanical  construction 
of  the  register. 

An  iron  base  about  fourteen  inches  square,  at  either 
corner  of  which  is  an  iron  rod  approximately  twenty-one 
inches  long  supporting  an  iron  top,  forms  a  frame  for 
the  register.  On  the  base  are  also  erected  the  standards 


HYDRAULIC  ENGINEERING  INSTRUMENTS         289 

which  support  the  recording  mechanism,  the  spools  for 
holding  the  paper  and  carbon  ribbon  and  the  driving 
mechanism. 


FIG.  112 

SECTION  OF  PAPER  TAPE,  SHOWING  PRINTED  RECORD  MADE 
ON  A  NO.  630  PRINTING  REGISTER 

The  recording  mechanism  consists  of  three  parallel 
type  wheels,  on  the  faces  of  which  are  raised  figures 
and  divisions  indicating  respectively  the  period  of  time 
from  one  to  twelve  hours  at  intervals  of  15  minutes,  as 
desired,  the  number  of  feet  from  zero  to  thirty-six,  and 
the  hundredths  of  .a  foot. 


290         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


FIG.   113 
No.  630  PRINTING  WATER  STAGE   REGISTER 

FRONT  VIEW,  SHOWING   CLOCK,  FLOAT  AND   WEIGHTS 


HYDRAULIC  ENGINEERING  INSTRUMENTS         291 

The  type  wheel  indicating  time  is  controlled  by  a 
weight  driven  clock  of  finest  construction,  with  full 
jeweled  escapement  and  compensated  to  endure  varia- 
tions of  climate  without  variation  in  its  regular  operation. 

The  two  type  wheels  indicating  heights  of  water  are 
moved  by  a  sprocket  wheel  connected  to  the  float  and 
counterweight  by  a  perforated  metal  band,  so  that  any 
change  in  the  height  of  water  is  immediately  indicated 
by  a  corresponding  movement  of  the  type  wheels. 

Four  reels  mounted  on  the  main  standard  of  the 
instrument  carry  and  receive  the  paper  strip  with  its 
carbon  backing  on  which  the  record  is  made,  and  which 
passes  over  the  type  wheels,  and  is  held  taut  by  the 
tension  of  a  weight  on  the  receiving  reel. 

Three  weighted  hammers,  pivoted  on  a  shaft  and 
with  cushioned  faces  opposite  the  center  of  the  type 
wheels,  are  controlled  in  their  action  by  a  saw-toothed 
cam,  moved  by  the  clock  in  such  a  manner  that  at  inter- 
vals of  15,  30  or  60  minutes  the  hammers  are  released 
and  strike  a  blow  on  the  type  wheels,  thus  making  on 
the  tape  covering  them  an  imprint  of  the  indicated  time, 
and  height  of  water. 

The  large  diameter  of  the  copper  float,  10  inches, 
enables  it  to  respond  immediately  to  any  variations  in 
the  height  of  the  water,  the  slightest  change  being  re- 
corded. Its  size  and  shape  render  it  extremely  sensitive, 
and  the  top  is  rounded  so  that  foreign  matter  cannot 
lodge  on  it  and  change  the  degree  of  immersion. 


292         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  frame  and  mechanism  as  above  described  are 
covered  by  a  metal  hood,  fitting  tightly  at  the  bottom 
in  a  rubber  gasket  and  having  at  the  top  a  clamp  nut 
which  may  be  secured  by  a  lock,  preventing  the  removal 
of  the  case  by  unauthorized  persons.  A  glass-covered 
opening  allows  an  easy  reading  of  the  clock,  which  may 
be  wound  from  the  outside  at  such  intervals  as  required 
without  the  removal  of  the  case  or  disturbance  of  the 
instrument. 

For  the  convenience  of  our  customers  we  publish  the 
"Manual  of  Gurley  Hydraulic  Engineering  Instru- 
ments." This  book  describes  in  detail  the  construction 
and  best  methods  of  installing  Gurley  Hydraulic 
Registers. 

GRAPHIC  WATER  STAGE  REGISTERS 

An  improved  Graphic  Register  is  shown  in  Fig.  114 
having  several  unique  and  valuable  features.  It  is  of 
simple  construction,  with  few  parts ;  is  designed  for  easy 
operation,  and  adapted  for  a  wide  range  of  conditions. 
Its  construction  is  such  that  no  lost  motion  will  develop 
from  continuous  service  and  it  can  be  operated  with 
minimum  care  and  expense. 

Vertical  scales  ranging  from  zero  to  twenty  feet 
are  supplied  and  time  scales  of  1  day,  4  days,  or  7  days 
can  be  furnished.  As  the  record  of  stage  is  made 
around  the  cylinder,  there  is  no  limit  to  the  number  of 
revolutions  possible,  and  hence  to  the  range  of  stage. 
Therefore,  it  is  advisable  to  use  as  low  a  range  as  possi- 


HYDRAULIC  ENGINEERING  INSTRUMENTS         293 


FIG.   114 
No.   633   GRAPHIC  WATER   STAGE   REGISTER 

SPRING-DRIVEN    CLOCK 


294         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

ble  and  obtain  a  more  accurate  reading  of  the  water 
stage.  If  occasionally  the  water  stage  is  above  the 
range  of  the  register,  no  trouble  will  be  experienced  in 
reading  the  water  level. 

Complete  descriptions  and  illustrations  of  our  hy- 
draulic equipment  is  furnished  in  "A  Manual  of  Gurley 
Hydraulic  Engineering  Instruments/'  which  will  be 
sent  upon  request. 

CONSTRUCTION 

The  Graphic  Water  Stage  Register  combines  admir- 
ably scientific  design  and  rugged  construction. 

An  extra  heavy,  spring  or  weight  driven  clock  is 
geared  to  two  time  screws  which  are  supported  at  each 
end.  Mounted  on  the  screws  is  a  carriage  holding  a 
weighted  pencil,  this  carriage  and  pencil  move  forward 
without  lost  motion  in  accord  with  the  turning  of  the 
clock  shaft. 

A  counterweighted  float  ten  inches  in  diameter  and 
three  and  one  half  inches  thick  operates  the  record  cylin- 
der either  directly  or  by  means  of  gears  according  to 
the  vertical  range  desired. 

The  whole  instrument  is  enclosed  in  a  sheet  metal 
cover  which  makes  it  waterproof  and  dust  proof. 


HYDRAULIC  ENGINEERING  INSTRUMENTS         295 

GURLEY  LONG  DISTANCE  GRAPHIC  WATER  STAGE 
REGISTER  AND  INDICATOR 

AS  the  result  of  several  years  experimenting  in  co- 
operation   with    a    number    of    leading    hydraulic 
engineers,   W.   &   L.   E.   Gurley   have   developed   a 
Long  Distance  Water  Stage  Register  which  is  the  most 
accurate,  efficient  and  reliable  instrument  of  its  type  on 
the  market. 

The  value  to  engineers  of  segregating  distant  gage 
readings  at  one  point  is  apparent.  In  power  plant 
operation,  particularly,  the  use  of  this  instrument  proves 
invaluable,  as  it  provides  means  of  determining  instantly 
the  varying  water  levels  at  distant  points,  and  thus  per- 
mits of  a  more  efficient  use  and  control  of  the  water 
available. 

The  outfit  consists  of  a  float-operated  Sender  which 
is  installed  at  the  gaging  station  and  by  which  the  vary- 
ing water  levels  are  transmitted  by  means  of  an  electric 
circuit  to  the  Receiver,  which  is  generally  located  in  the 
power  house  or  in  the  office  of  the  engineer  responsible 
for  the  efficient  operation  of  the  plant. 

The  Receiver  may  consist  of  an  indicating  device 
only,  or  it  may  include  a  Register  making  a  graphic 
record,  or  the  apparatus  may  comprise  a  combination  of 
both,  as  desired.  Furthermore,  it  is  possible,  with  one 
Sender,  to  operate  several  Receivers,  of  the  indicating 
or  recording  type,  at  different  locations. 


296         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

The  Sender  and  the  Receiver  are  of  simple  construc- 
tion and  high  grade  workmanship  and  are  very  positive 
and  uniform  in  their  operation. 


FIG.  115 

No.  637  LONG  DISTANCE 
GRAPHIC  WATER  STAGE  REGISTER 


In  modern  hydraulic  practice  it  is  often  desirable  to 
record  or  indicate  in  the  office  or  power  house,  the  water 
stage  at  some  distant  point. 

Gurley  Long  Distance  Registers  and  Indicators  are 
electrically  operated  and  will  record  or  indicate  accur- 
ately the  fluctuations  of  any  liquid  level  at  any  distance. 


HYDRAULIC  ENGINEERING  INSTRUMENTS         297 

THE  SENDER,  located  at  the  point  where  the  water 
stage  is  to  be  measured,  is  operated  by  a  float  and 
counterweight  similar  to  those  used  on  our  other  regis- 
ters. It  is  equipped  with  two  electrical  contacts,  one 
of  which  closes  for  a  fraction  of  a  second  every  time  the 
float  rises,  the  other  when  the  float  falls  1/20  of  a  foot. 
These  contacts,  which  were  developed  in  the  Gurley 
factory,  have  been  subjected  to  tens  of  thousands  of 
tests  with  heavy  load  at  120  volts,  without  any  failure 
or  even  a  sign  of  deterioration. 

THE  RECEIVER  consists  of  one  of  our  No.  633  Graphic 
Registers,  but  modified  so  that  the  record  cylinder  is 
operated  by  magnets  instead  of  directly  by  the  float. 
The  drum  is  turned  by  means  of  gears  and  a  ratchet 
wheel  which  is  operated  by  two  pairs  of  powerful  mag- 
nets, one  for  rising,  the  other  for  falling  water.  The 
operating  arms  which  are  attached  to  the  magnet  arma- 
tures turn  the  ratchet  wheel  one  notch  each  time  either 
magnet  is  energized.  These  arms  also  carry  interlocking 
stops  which  positively  prevent  the  wheel  from  turning 
more  than  one  notch,  until  the  magnet  is  released  and 
ready  for  the  next  step.  The  rear  end  of  the  drum 
carries  a  dial  and  pointer,  so  that  the  water  stage  may 
be  read  directly  without  looking  at  the  chart. 

The  circuits  necessary  to  connect  the  Sender  and 
Receiver  may  consist  either  of  3  wires  or  2  wires  and  a 


298         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

"ground"  return.  A  satisfactory  circuit  may  be  obtained 
by  leasing  a  private  telephone  line  of  2  wires.  The 
current  required  to  operate  the  receiver  is  0.1  ampere 
and  this  flows  through  the  line  for  only  a  fraction  of  a 
second  when  the  contact  is  made.  At  all  other  times 
the  circuits  are  open.  The  resistance  of  the  coils  is  40 
ohms.  The  power  may  be  supplied  by  dry  cells  or 
storage  batteries.  For  long  distances  it  is  better  to  take 
it  from  a  110  volt  D.  C.  power  or  storage  battery  line, 
if  continuously  available  throughout  the  24  hours  of  the 
day.  A  lamp  placed  in  the  circuit  will  cut  down  the 
current  to  the  proper  amount,  that  is,  0.1  ampere.  The 
power  may  be  connected  into  the  circuit  at  any  point 
in  the  line. 

Any  number  of  Receivers  or  Indicators  may  be  used 
on  the  circuit  for  one  Sender. 

Blue  prints  showing  the  necessary  wiring  connections 
will  be  furnished  upon  request. 

THE  LONG  DISTANCE  WATER  STAGE  INDICATOR 
answers  the  purpose  where  a  record  of  the  water  level 
is  not  desired  but  only  an  indication  of  the  level  at  some 
distant  point.  This  operates  with  the  same  Sender  and 
circuits  described  above  for  the  Long  Distance  Graphic 
Water  Stage  Register.  Instead  of  the  No.  633  Register, 
a  large  dial  1 2  inches  in  diameter,  with  a  moving  pointer, 
is  operated  by  electro-magnets  and  a  ratchet  wheel,  in 
the  same  manner  as  the  Long  Distance  Register.  This 
dial  shows  the  height  of  the  water  at  the  distant  gage 


HYDRAULIC  ENGINEERING  INSTRUMENTS          299 

house,  at  any  instant.  A  larger  dial  can  be  furnished 
if  desired.  Prices,  which  depend  upon  the  size,  will  be 
quoted  upon  application. 


FIG.  116 

No.  638  FLOAT  OPERATED  SENDER,  FOR  LONG 
DISTANCE  GRAPHIC  REGISTER 

This  Indicator  may  also  be  put  on  the  same  circuit 
with  a  Register.  In  many  cases  it  will  be  desirable  to 
have  an  Indicator  in  the  power  plant  for  the  information 


300 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


of  the  operator,  while  the  Register  may  be  placed  in  the 
office  of  the  chief  engineer,  where  the  records  will  be 
kept  and  studied. 

Detailed  information  concerning  the  solution  ol 
special  gaging  problems  of  hydraulic  engineers  will  be 
furnished  upon  request. 


FIG.  117 
No.  639  LONG  DISTANCE  INDICATOR  WITH  12"  DIAL 


INDICATING  GAGE  No.  639-A  will  be  found  a  great 
help  in  the  checking  of  gage  heights  in  stilling  wells  in 
which  automatic  recording  gages  are  installed.  It  can 
be  used  also  wherever  water  levels  are  to  be  observed. 

This  instrument  is  designed  to  replace  the  ordinary 
hook,  chain  and  staff  gages  where  very  accurate  readings 
are  required.  The  sprocket  wheel  is  one  foot  in  cir- 


HYDRAULIC  ENGINEERING  INSTRUMENTS         301 

cumference  and  is  divided  into  100  parts,  and  the  feet 
may  be  read  on  the  counter  up  to  100.  This  gage  will 
be  furnished  with  or  without  the  float. 


FIG.  118 
No.  639-A  INDICATING  GAGE 


302         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

PRECISION   BALANCE 

THE  GURLEY  PRECISION  BALANCE  is  the  highest 
development  of  a  weighing  instrument  and  is  constructed 
strictly  in  accordance  with  the  best  scientific  principles, 
all  parts  being  of  a  sufficient  strength  to  support  an 
overload  of  100%  without  perceptible  strain. 

The  capacity  of  the  balance  is  fifty  pounds  or  twenty- 
five  kilograms  in  each  pan,  with  a  sensibility  of  one 
grain  or  .06  gram  at  full  load.  The  beam  is  of  a 
special  aluminum  alloy  which  will  remain  constant  under 
all  conditions,  and  is  equipped  with  a  vertically  adjust- 
able weight  by  which  the  sensibility  reciprocal  can  be 
altered  to  suit  the  convenience  of  the  operator.  The 
pillar  is  of  bronze  with  positive  beam  and  pan  arrest- 
ment  and  with  pointer  swinging  inside  of  the  pillar  over 
a  horizontal  scale,  back  of  which  is  placed  a  mirror  to 
facilitate  the  readings.  All  bearings  are  made  of  agate 
and  the  knife  edges  are  of  the  best  hardened  steel.  The 
pan  hangers  are  of  bronze  and  aluminum,  and  the  pans 
are  of  nickel  plated  brass.  The  base  is  of  highly  pol- 
ished oak  or  mahogany,  with  attached  spirit  level  and 
four  leveling  screws. 

The  base  is  about  40  inches  long  and  15  inches  wide. 
The  overall  height  of  the  Balance  is  about  40  inches. 

In  addition  to  the  balance  illustrated  above,  we  also 
manufacture  Precision  Weights  and  Measures  used  as 


PRECISION   BALANCE 


303 


official  standards.  These  are  of  the  highest  degree  of 
accuracy,  and  are  guaranteed  to  conform  to  the  specifi- 
cations of  the  National  Bureau  of  Standards.  A  certifi- 
cate of  test  from  this  bureau  will  be  furnished  when 
desired. 


FIG.   119 
No.  9570  PRECISION  BALANCE 


304         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

We  have  made  official  weights  and  measures  for  the 
Bureau  of  Standards  and  for  practically  all  of  the  De- 
partments of  Weights  and  Measures  in  this  country; 
also  for  China,  the  Philippine  Islands,  Porto  Rico  and 
Haiti.  We  are  prepared  to  furnish  weights  and 
measures  to  conform  to  the  standards  of  any  foreign 
country. 

A  bulletin  describing  the  weights,  measures,  and 
Sealer's  equipment  will  be  sent  upon  request. 


GENERAL  INFORMATION  305 

GENERAL   INFORMATION 
EXTENT  OF  OUR  BUSINESS 

FOR  many  years  our  facilities  for  the  manufacture  of 
Engineering  and  Surveying  Instruments  have  been 
far  superior  to  those  of  any  other  similar  establish- 
ment in  the  world.    They  are  being  constantly  increased 
by  the  introduction  of  new  machinery  and  tools. 

We  make  in  our  own  factory  the  lenses  for  the  tele- 
scopes of  our  instruments,  the  platinum  filament  for  the 
cross  wires  and  stadia  wires,  the  glass  vials  for  the 
levels,  the  wooden  boxes  in  which  the  instruments  are 
carried,  the  leather  cases  and  straps  for  these  boxes,  as 
well  as  the  castings  and  all  other  metal  parts  of  the 
instruments  themselves. 

Thousands  of  our  instruments  have  been  distributed 
to  all  parts  of  the  United  States,  Canada,  Mexico,  Cen- 
tral America,  West  Indies,  South  America,  China, 
Japan,  Australia,  Africa,  India  and  other  foreign 
countries. 

OUR  GUARANTEE 

All  instruments  of  our  own  make  are  examined  and 
tested  before  being  shipped,  and  are  sent  to  the  pur- 
chaser adjusted,  ready  for  immediate  use.  They  are 
warranted  correct  in  all  their  parts  —  we  agreeing  in 
the  event  of  any  original  defect  appearing  after  reason- 
able use,  to  repair  or  replace  with  new  and  perfect 


306         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

instruments,  promptly  at  our  own  cost,  express  charges 
included;  or  we  will  refund  the  money  and  the  express 
charges  paid  by  the  purchaser. 

It  sometimes  happens  in  a  business  as  large  and 
widely  extended  as  ours  that  instruments  reach  our 
customers  in  bad  condition,  owing  to  careless  transporta- 
tion, or  to  defects  escaping  the  closest  scrutiny  of  our 
inspectors.  We  consider  the  retention  of  such  instru- 
ments by  the  purchaser  an  injury  very  much  greater  to 
us  than  to  himself.  We  also  consider  that  a  sale  is  not 
completed  until  the  purchaser  is  satisfied  in  every  detail. 

TRIAL  OF  INSTRUMENTS 

If  requested  to  do  so,  we  will  ship  to  the  express 
station  nearest  the  person  giving  the  order  and  will  in- 
struct the  express  agent  to  collect  the  amount  of  our  bill 
and  hold  the  money  three  days.  This  will  give  the 
purchaser  an  opportunity  to  test  the  instrument  in  the 
field  and  if  it  is  not  found  as  represented,  he  may  return 
it  to  the  express  agent  who  will  refund  the  full  amount 
paid,  including  transportation  charges. 

This  privilege  of  trial  applies  only  to  our  large 
instruments  such  as  Transits,  Levels,  Compasses,  etc., 
is  not  given  unless  requested,  and  is  allowed  only  in  the 
United  States.  Privilege  of  trial  is  not  allowed  by  the 
Great  Northern  or  Southern  Express  Companies.  All 
express  companies,  however,  will  allow  examination  of 
instruments  at  their  offices,  if  the  shipper  requests  it  for 
the  purchaser. 


GENERAL  INFORMATION  307 

ORDERING 

In  ordering  always  give  the  Catalogue  Numbers  of 
the  instruments  and  accessories  selected. 

If  full  particulars  concerning  each  item  accompany 
the  order,  delay  will  often  be  avoided,  as  it  will  proba- 
bly be  unnecessary  for  us  to  write  you. 

If  no  shipping  directions  are  given,  we  will  always 
ship  by  the  quickest  and  safest  method. 

When  any  articles  can  be  sent  safely  by  mail,  we  have 
printed  the  approximate  cost  of  postage  so  that,  by  re- 
mitting with  the  order  the  cost  of  the  article  and  the 
postage,  the  goods  can  be  sent  at  small  expense.  Should 
the  amount  sent  exceed  the  actual  postage,  the  balance 
will  be  returned. 

All  articles  can  be  insured  at  an  extra  cost  which 
varies  according  to  the  value  of  the  package.  For  de- 
tails see  Parcel  Post  Regulations. 

PACKING  AND  DELIVERY 

Each  of  our  Transits,  Levels  and  Surveyors  Com- 
passes is  packed  in  a  well  finished  mahogany  case, 
furnished  with  lock  and  key,  and  leather  strap  for 
convenience  in  carrying. 

When  sent  to  the  purchaser  the  mahogany  cases  are 
carefully  enclosed  in  outside  packing  boxes  of  pine,  made 
a  little  larger  on  all  sides  to  receive  elastic  packing 
material. 


308         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

We  make  no  charge  for  packing  boxes  or  packing, 
and  our  instruments  are  delivered  F.  O.  B.  Troy,  N.  Y., 
to  the  express  company  or  freight  house. 

Charges  for  transportation  are  in  all  cases  to  be  paid 
by  the  purchaser,  we  guaranteeing  the  safe  arrival  of  our 
goods  at  the  destination  indicated  at  the  time  of  ship- 
ment. 

TERMS  OF  PAYMENT 

Terms  of  payment  are  uniformly  cash,  and  we  have 
but  one  price,  whether  ordered  in  person  or  by  mail. 
Our  prices  are  as  low  as  instruments  of  first  quality  can 
be  made. 

Remittances  may  be  made  by  a  cashier's  bank  draft, 
payable  to  our  order,  or  by  Express  Company  or  Post 
Office  money  order  payable  at  Troy,  N.  Y.  These  may 
be  sent  by  mail  with  the  order  for  the  instrument,  and 
if  lost  or  stolen  on  the  route  can  be  replaced  by  a  dupli- 
cate, and  without  additional  cost. 

The  customer  may  also  send  the  money  in  advance 
by  registered  mail,  or  by  the  express  agent,  or  instruct 
us  to  forward  the  shipment  C.  O.  D.  Goods  ordered  for 
shipment  to  foreign  countries  must  be  paid  for  in  ad- 
vance of  shipment. 

Customers  ordering  instruments  and  desiring  changes 
in  construction  from  our  regular  patterns,  must  make  a 
payment  in  advance  when  ordering  of  fifty  per  cent,  of 
the  price. 


GENERAL  INFORMATION  309 


INSTRUMENTS  FOR  FOREIGN  COUNTRIES 


FIG.  120 

Instruments  packed  for  foreign  shipment  which  are 
to  have  ocean  passage  are  wrapped  in  waterproof  mater- 
ial and  enclosed  in  strong  packing  boxes  which  are 
strengthened  and  protected  by  special  band  wire. 

The  cash  for  all  orders  for  foreign  shipments  by 
steamship  must,  in  every  case,  accompany  the  order;  and 
if  it  is  desired  that  we  attend  to  the  shipment  of  the 
instruments,  the  remittance  must  be  made  ten  per  cent, 
more  than  the  catalogue  price  of  the  instruments  if  the 
order  amounts  to  $250  or  less;  or  eight  per  cent,  more 
than  catalogue  price  if  the  order  amounts  to  from  $300 
to  $500;  or  six  per  cent,  more  than  catalogue  price  if  the 
order  amounts  to  from  $600  to  $1,000. 


310         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

This  extra  remittance  is  to  cover  cost  of  shipping 
charges,  freight  and  insurance,  which  must  always  be 
paid  in  advance  on  all  shipments  except  those  consigned 
to  Canada  and  some  parts  of  Mexico. 

If  the  amount  remitted  is  more  than  enough  to  cover 
these  expenses,  the  balance  will  be  returned  to  the  pur- 
chaser with  the  receipted  bill  and  bill  of  lading,  unless 
we  are  directed  to  hold  it  to  his  credit. 

Remittances  must  be  made  by  bank  draft  on  New 
York  City  or  London,  England,  and  such  drafts  can  be 
purchased  in  any  of  the  large  cities  of  the  different 
countries. 

Our  registered  cable  address  is  "GURLEY,  TROY." 
Use  Bentley's,  Western  Union,  A.  B.  C.  Fifth  Edition, 
or  Lieber's  Codes.  See  Private  Cable  Code  on  pages 
315  to  323. 

REPAIR  OF  INSTRUMENTS 

Each  year  we  receive  hundreds  of  instruments  of  our 
own  and  other  makes  sent  to  us  for  refitting  and  repairs. 

We  advise  our  customers  who  have  instruments  in 
need  of  repairs  to  send  them  directly  to  us,  as  our  facil- 
ities enable  us  to  do  the  work  economically  and  promptly. 

They  should  always  be  placed  in  their  own  boxes, 
and  then  enclosed  in  an  outside  packing  case,  at  least 
an  inch  larger  in  all  its  dimensions,  and  the  space  be- 
tween the  two  filled  with  paper  wadding,  hay  or 
shavings. 


GENERAL  INFORMATION  311 

The  owner's  name  and  address  should  always  appear 
on  the  package  and  a  note  specifying  the  repairs  needed 
should  accompany  the  instrument.  A  letter  should  also 
be  sent  by  mail  to  us,  giving  not  only  directions  as  to  the 
repairs,  but  also  stating  when  the  return  of  the  instru- 
ment is  required,  and  the  precise  location  to  which  it 
should  be  forwarded. 

It  should  also  be  remembered  that  each  instrument 
is  made  to  fit  its  own  spindle,  and  no  other ;  and  there- 
fore the  leveling  head  complete  (centers  and  spindle) 
should  always  be  sent  with  it. 

The  tripod  legs  and  brass  head  in  which  they  are 
inserted  need  not  be  sent  unless  in  need  of  repairs. 

When  requested  to  do  so,  we  will  furnish  an  estimate 
of  the  cost  of  the  repairs  on  any  instrument  sent  us, 
before  beginning  the  work. 

SELECTION  OF  INSTRUMENTS 

For  ordinary  land  surveying,  the  Vernier  Compass 
is  required  where  the  variation  of  the  needle  is  to  be 
allowed,  as  in  retracing  the  lines  of  an  old  survey,  etc. 

When,  in  addition  to  the  variation  of  the  needle, 
local  attraction  must  be  taken  into  account  and  angles 
taken  independently  of  the  needle,  an  instrument  with  a 
graduated  limb  must  be  used,  and  for  this  purpose  a 
Compass  with  horizontal  limb  is  required.  See  No.  294. 

For  municipal  engineering,  railroad  and  highway 
construction,  bridge  building,  drainage  and  irrigation 
work,  selection  should  be  made  from  our  Precise  Tran- 


312         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

sits  Nos.  6-A  to  10- A,  26-A  to  29-A,  Light  Mountain 
Transits  Nos.  26  to  29;  and  Engineers  Wye  Levels 
Nos.  375  to  378. 

The  Light  Mountain  Transits  (regular  and  Precise 
types)  are  also  ideal  instruments  for  surveys  of  mining 
claims,  especially  in  high  elevations,  and  for  surveys  of 
mines  in  general. 

For  United  States  Public  Land  Surveys  an  instru- 
ment with  the  Solar  Attachment  is  required  and  the 
Solar  Transit  is  used;  see  Nos.  30- A,  32-A  and  23-A. 

No.  18-A  "Hell  Gate  Model"  Precise  Transit  is 
capable  of  executing  triangulation  surveys  demanding 
the  highest  degree  of  accuracy  and  refinement. 

The  various  Plane  Table  Outfits  have  a  recognized 
utility  for  topographical  surveys  and  map  drawing. 

The  Current  Meters  are  almost  indispensable  in 
measuring  the  velocity  of  the  flow  of  water  in  harbors, 
rivers,  small  streams  and  irrigation  ditches. 

The  Automatic  Water  Stage  Registers  are  used  for 
determining  the  variations  in  the  height  or  stage  of  the 
water  in  connection  with  water  power  development,  irri- 
gation investigations  and  sewage  discharge. 

The  Hook  Gage  is  utilized  for  ascertaining  the  depth 
of  water  flowing  over  weirs,  etc. 

The  Architects  Level  is  employed  in  laying  out 
buildings,  determining  the  level  of  their  floors,  sills  and 
windows,  and  in  the  general  work  of  the  builder  and 
contractor. 


GENERAL  INFORMATION  313 

The  Explorers  Transit,  the  Reconnoissance  Transit, 
the  Explorers  Level  and  the  various  forms  of  Pocket 
Compasses  are  designed  for  preliminary  surveys  where 
extreme  lightness  and  portability  are  required. 

When  iron  ores  are  to  be  traced,  the  Dip  Compass 
and  the  Dial  Compass  are  used. 

We  do  not  make  any  instrument  by  which  veins  of 
gold  and  silver  can  be  traced,  or  the  presence  of  these 
metals  detected. 

EXCHANGING  OLD  INSTRUMENTS 

Correspondence  is  solicited  relating  to  exchanging 
old  instruments  of  our  make  for  those  of  the  latest 
patterns. 

We  are  constantly  making  such  exchanges  to  the 
entire  satisfaction  of  our  customers  and  if  the  old  instru- 
ments are  salable  as  second-hand,  after  being  rebuilt 
and  refimshed,  a  liberal  allowance  is  made. 

INVITATION  TO  VISIT  OUR  FACTORY 

A  cordial  invitation  is  extended  to  our  customers  to 
visit  our  Factory  in  Troy,  N.  Y.  Opportunities  are 
thus  had  for  examining  the  various  instruments  we 
make  and  for  observing  the  processes  of  manufacture. 
Visitors  who  call  on  us  are  greatly  impressed  with  the 
size  of  our  establishment  and  also  with  the  elaborate 
equipment  which  is  required  to  produce  high  grade 
instruments. 


314         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

LITERATURE 

We  publish  a  variety  of  attractive  bulletins  contain- 
ing special  information  relative  to  our  products.  They 
will  be  supplied  to  our  correspondents  who  express  an 
interest  in  or  a  desire  for  some  particular  instrument. 

GURLEY  SOLAR   EPHEMERIS 

The  Solar  Ephemeris  is  published  annually.  It  is 
an  abridgment  of  the  Nautical  Almanac,  issued  by  the 
United  States  Government,  and  contains  a  Table  of 
Mean  Refractions  in  Declination  and  Tables  of  Times 
of  Elongation,  Culmination  and  Azimuths  of  Polaris. 
It  can  be  conveniently  carried  in  the  vest  pocket.  A 
copy  will  be  sent  postpaid  to  any  engineer  or  surveyor, 
on  request. 


PRIVATE  CABLE  CODE 


315 


PRIVATE  CABLE  CODE 

CABLE  CODE  :  "GURLEY" 

Use  Bentley's,  Western  Union,  Lieber's;  or 
A.  B.  C.  5th  Edition,  Codes 


Cat.  No. 

6-A 

7-A 

8-A 

9-A 
10-A 
10-A-3 
18-A 
23-  A 
26-A 
27-A 
28-A 
29-A 
30-A 
32-A 
20-A 
21-A 
22-A 
23-A 
24-A 
25 
26 
27 
28 
29 
30 
102 
103 


131 

135-B 

136 

137 

138 


Description  Code  Word 

Precise  Transit,  Engineers    size  ..........................    Abaab 

Precise  Transit,  Engineers   size  ..........................    Ababa 

Precise  Transit,  Engineers   size  ..........................    Ababs 


Precise  Transit,  Engineers   size 

Precise  Transit,  Engineers    size 

Precise  Transit,  with  Three-Screw  Leveling   Head 

Precise  Transit,  Hell    Gate    Model 

Precise  Transit,  Mountain    size 

Precise  Transit,  Mountain 

Precise  Transit,  Mountain 

Precise  Transit,  Mountain 

Precise  Transit,  Mountain 

Precise  Transit,  Mountain 


Abaca 
Abacy 
Abagn 
Abago 
Abaha 
Abahi 


size     .  .  . 

size     ..........................  Abahl 

size     ..........................  Abahs 

size     ..........................  Abaib 

size     ..........................  Abaig 

Precise  Transit,  with    Telescopic    Solar    ...................  Abail 

Explorers  Precise  Transit     ...............................  Abaek 

Explorers  Precise  Transit     ...............................  Abaen 

Explorers  Precise  Transit     ...............................  Abaer 

Explorers  Precise  Transit     ...............................  Abaet 

Explorers  Precise  Transit     ...............................  Abagu 

Light  Mountain  or  Mine  Transit     .........................  Atimy 

Light  Mountain  or  Mine  Transit      .........................  Atjip 

Light  Mountain  or  Mine  Transit    .  .........................  Atkir 

Light  Mountain  or  Mine  Transit     ..........................  Atler 

Light  Mountain  or  Mine  Transit     .........................  Atmar 

Light  Mountain  or  Mine  Transit     .........................  Atnas 

Reconnoissance  Transit     .................................  Avseb 

Reconnoissance  Transit    .................................  Abalm 

Limb  I    ................  ,  .................................  Abaip 

Limb  IV    ................................................  Abaiy 

Variation    Arc    ..........................................  Arbuc 

Vertical  Circle     ..........................................  Arfen 

Vertical  Circle     ..........................................  Arfid 

Vertical  Circle     .........................................  Argog 

Vertical  Circle    .                                                                               .  Arins 


316         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Cat.  No.  Description                                                       Code  Word 

139  Vertical  Circle Abajo 

139-A        Vertical  Arc     Arkal 

139-B        Vertical  Arc     Arkon 

140  Vertical  Arc Arlik 

141  Aluminum    Guard    Armil 

145  Level   on   Telescope    Arnon 

146  Reversion    Telescope   Level    Arobs 

148  Clamp   and   Tangent    Aroms 

149  Beaman  Stadia  Arc     Arpal 

149-A        Beaman  Stadia  Arc     Abake 

149-B        Beaman  Stadia  Arc     Abaks 

149-C         Beaman  Stadia  Arc    Abaku 

150  Gradienter    Arram 

151  Stadia  Wires,  Adjustable      , Abald 

152  Stadia  Wires,  Fixed     Abalk 

154  Dust    Guard    Abalo 

155  Pinion    Movement    Abalt 

157  Sights  on  Telescope     Arren 

158  Sights  on  Standards     Arrot 

160  Detachable  Side   Telescope   and   Counterpoise    Arsan 

161  Detachable  Riding  Telescope     Artap 

165  Reflector  for  Transit  Cross  Wrires     Artot 

166  Reflector  for  Level  Cross  Wires     Arvit 

167  Elbow    Eyepiece Abaly 

168  Diagonal    Prism    Arwet 

169  Eyepiece   Cap    Abalu 

170  Plummet  Lamp    Arzub 

ISO  Attached  Magnifier    Asbid 

181  Attached  Microscopes     Abamo 

182  Attached  Microscopes     Abams 

185  Limb  Graduation     Ascog 

186  Limb  Graduation     Asdig 

187  Vertical  Circle  Graduation    Asels 

188  Vertical  Circle  Graduation    Asgle 

189  Vertical  Circle  Graduation    Abamu 

190  Burt   Solar   Attachment    Ashik 

192  Solar    Screen    Abana 

193  Patent    Latitude    Level    Asilt 

196  Striding    Level Askon 

197  Adjusting    Bar    Abang 

226  Vernier    Compass    Agwen 

241  Leveling  Adopter    Afbir 

242  Leveling  Head Afcot 


PRIVATE  CABLE  CODE  317 


Cat.  No.  Description                                                       Code  Word 

262  Telescopic   Sight    Apbat 

20.")  Vertical  Circle  for  No.   262  Telescopic  Sight    Apfob 

266  Level  on  Telescope  for  No.  262  Telescopic  Sight    Aphic 

267  Clamp  and  Tangent  for  No.   262  Telescopic  Sight   Aplad 

268  Offset  Standard  and  Counterpoise  for   No.   262  Telescopic 

Sight    Apost 

285  Pocket  Compass  with   Limb    Addip 

294  Compass  with  Limb  and  Telescope    Abans 

300  Pocket  Vernier  Compass    Afrad 

305  Pocket  Vernier  Compass'    Afseg 

325  Clamp    and   Tangent    Agbet 

326  Rack   and  Pinion  Movement    Agcat 

327  Leveling  Adopter     Agdix 

328  Leveling  Head Agern 

835  Geologists    Compass    Afnid 

341  Dip  Compass     Afkob 

341-A        Dip  Compass     Aflam 

350  Dial  Compass      Afirl 

375  Engineers  Wye  Level     Akary 

377  Engineers  Wye  Level     Akdul 

378  Engineers  Wye  Level    Akgun 

381  Architects  Level     Ajrot 

384  Explorers  Level     Abaoh 

400  Transit  Tripod    Axnig 

401  Transit  Tripod    Axots 

405  Transit  Tripod    Axrul 

406  Transit  Tripod     Axtil 

410  Transit  Tripod    Axvim 

411  Transit  Tripod     Axyan 

412  Transit  Tripod     Abaok 

415  Compass  Tripod     Awact 

41 6  Compass  Tripod     Awder 

420  Compass  Tripod     Awflt 

421  Compass  Tripod     Awify 

425  Compass  Tripod     Aworl 

426  Compass  Tripod     Awrif 

430  Level  Tripod     Axbar 

431  Level  Tripod    Axcet 

435  Level  Tripod    Axdox 

436  Level  Tripod     Axfoy 

440  Level  Tripod    Axgub 

441  Level  Tripod     Axhob 

443  Level  Tripod     Abapa 


318         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Cat.  No.  Description                                                       ('ode  Word 

450  Plain  Plummet    ....    Abaph 

452  Plain  Plummet     Abapt 

454  Plain  Plummet    Abapy 

456  Plain  Plummet Abarb 

458  Plain  Plummet     Abarc 

460  Plain  Plummet     Abarf 

465  Adjustable    Plummet    Abari 

471  Iron   Spads    Abarm 

472  Stake  Tacks    Vbarp 

473  Stake  Tacks    Abars 

474  Plummet  Cord     Abaso 

475  Leather  Case    Abasp 

476  Leather  Case Abast 

478  Leather  Case Abasy 

479  Leather  Case     Abata 

480  Leather  Case     Abath 

485  Leather  Case    Abaty 

486  Leather  Case    Abaud 

487  Leather  Case     Abaur 

490  Leather  Pouch     Abaux 

491  Leather  Pouch    Abauz 

492  Leather  Pouch    Abauj 

494  Tripod  Case    Abava 

496  Tripod  Case     Abavi 

497  Tripod  Case    Abavy 

498  Leather  Field  Bag    Abawi 

If   metric  graduations   are  wanted,    specify   "METRIC" 
after  the  code  word  for  the  Red. 

500  Philadelphia  Rod    Albol 

500-A        Philadelphia  Rod     Abaxo 

500-B        Philadelphia  Rod     Alcun 

500-R        Service  Rod    Abayu 

501  Philadelphia  Rod     Aldon 

501 -B        Special    Self-Reading    Rod    Alfop 

502-A        Philadelphia  Mining  Rod     • Algor 

504  Troy  Rod     Alimb 

505  New  York  Rod     Aljer 

510  Architects  Rod    Alnew 

511  Architects  Rod     Alond 

513  Telemeter  Rod    Alrob 

514  Telemeter  Rod    Alsay 

514-B        Stadia  Rod    Abaye 

514-C        Stadia  Rod Abayr 

514-D        Stadia  Rod     Abayt 


PRIVATE  CABLE  CODE  319 


Cat.  No.  Description                                                     Code  Word 

514-E        Stadia  Rod     Abaza 

515  Telescopic  Rod     Altic 

510  Cross  Section  Rod Alubs 

517  Slip-Jointed  Rod    Abbej 

518-A        Plain  Rod    Alvof 

518-B        Plain  Rod    Alwed 

519-A        Plain  Rod     Amand 

519-B        Plain  Rod Ambin 

520-A        Plain  Rod    Amcus 

520-B        Plain  Rod    , Amdut 

521-B        Plain  Rod     Amfis 

522-A        Plain  Rod     Amgit 

522-B        Plain  Rod    Amhow 

522-C         Plain  Rod     Amild 

524-A         Plain  Rod,  4  ply     Amkoy 

525-B        Flexible  or  Pocket  Leveling  Rod     Ampod 

52G-A        Flexible  or  Pocket  Leveling  Rod     Amrid 

52G-B        Flexible  or  Pocket  Leveling  Rod    Amsed 

527  Flexible  or  Pocket  Leveling  Rod    Am  tad 

528  Flexible  or  Pocket  Leveling  Rod     Amudy 

530  Combined  Leveling  Pole  and  Flagstaff     Akhon 

531  Combined  Leveling  Pole  and  Flagstaff     Akkip 

534  Wood  Flagstaff     Abazi 

535  Wood  Flagstaff    Abazy 

53G  Wood  Flagstaff    Abbac 

537-A        Screw-Jointed  Wood  Flagstaff     Abbaf 

537-B        Screw-Jointed  Wood  Flagstaff     Abbal 

537-C         Screw- Jointed  Wood  Flagstaff     Abbam 

537-D        Screw-Jointed  Wood  Flagstaff     Abbap 

538- A        Screw-Jointed  Wood  Flagstaff     Abbas 

538-B        Screw-Jointed  Wood  Flagstaff     Abbaw 

540-A        Steel  Ranging  Pole    Abbed 

540-B        Steel  Ranging  Pole Abbeh 

541  Iron  Tubnlar  Ranging  Pole     Abbek 

543  Iron  Tubular  Ranging  Pole     Abben 

544  Iron  Tubular  Ranging  Pole     Abbet 

550-R        Gurley  Precise  Rod     Abbig 

551-R        Molitor  Precise  Rod     Abbif 

552-R        Tape  Leveling  Rod     Abbic 

545  Rod  Level     Amnez 

546  Rod  Level    Amnit 

547  Rod  Level    Amnor 

548  Rod  Level    Abbev 

570  Johnson  Plane  Table  Movement     Abbil 

570-A        Johnson  Plane  Table  Movement     Abbim 


320         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Cat.  No.  Description  Code  Word 

571  Johnson  Plane  Table  Movement    Abbip 

573  Drawing  Board    Abbis 

573-A  Drawing  Board Abbiy 

573-B  Drawing  Board Abboh 

573-T  Drawing  Board     Abbot 

573-X  Drawing  Board     Abbok 

574  Plumbing  Arm  and  Plummet   Abbon 

575  Combined   Compass   and   Levels    Abbor 

57G-B  Plane  Table  Outfit     Abboz 

576-C  Plane  Table  Outfit     Abbud 

584-B  Telescopic  Alidade    Abnot 

584-C  Telescopic  Alidade     Abbuk 

585  Box  Compass    Abome 

586  Traverse  Plane  Table  Outfit Ankud 

587  Traverse  Plane  Table  Movement  and  Drawing  Board     Anlic 

588  Box  Compass    Anmid 

589  Ruler  Sight  Alidade     Anoby 

590-A  Pocket  Sight  Alidade    Anpad 

590-B  Pocket  Sight  Alidade    Anruk 

592-C  Explorers  Alidade    Abcag 

592-D  Explorers  Plane  Table  Outfit    Abcal 

592-F  Explorers  Plane  Table  Outfit    Abeam 

592-H  Explorers  Plane  Table  Outfit     Abcap 

594  Army  Sketching  Case     Abcas 

596  Fiala  Scout  Sketching  Case    Abced 

609  Electric  Register  for  Current  Meters     Acrub 

616  Current  Meter    Acvod 

617  Current  Meter    Acwid 

619  Time  Recorder  or  Stop  Watch    Adaf t 

621  Current  Meter     Adbel 

623  Current  Meter    Adbot 

628  Hook  Gage    Abcek 

630  Printing  Water  Stage  Register    Anvel 

632  Tape  Reel Anwat 

633  Graphic  Water  Stage  Register    Abcet 

634  Graphic  Water  Stage  Register    Abcev 

634-A  Graphic  Water  Stage  Register     Abcic 

636  Graphic  Water  Stage  Register    Abcif 

637  Long  Distance  Register    Abeik 

638  Long  Distance  Sender    Abeil 

639  Long  Distance  Indicator    Abein 

639-A  Indicating  Gage    Abeir 

640  Monocular  Hand  Level     Aklut 

643  Locke  Hand  Level    Akpow 

646  Abney  Hand  Level    Aksoy 


PRIVATE  CABLE  CODE  321 


Cat.  No.  Description  Code  Word 

G46-A  Abney  Hand  Level    Abcil 

647  Abney  Hand  Level    Abcim 

647-A  Abney  Hand  Level Abcip 

648  Abney  Hand  Level    Abcuv 

649  Stadia  Hand  Level    Aktye 

650  Iron  Chain     Abcis 

631  Iron  Chain    Abciy 

652  Iron  Chain Abcod 

653  Iron  Chain     Abcob 

656  Steel  Chain     '. Abcok 

658  Steel  Chain     Abcon 

662  Steel  Chain    Abcox 

670  Brazed  Steel  Chain    Abpit 

671  Brazed  Steel  Chain    Abret 

672  Brazed  Steel  Chain    Absat 

673  Brazed  Steel  Chain     Abtoy 

690  Vara  Chain    Abcur 

691  Vara  Chain     About 

694  Vara  Chain    Abcux 

695  Vara  Chain     Abcyb 

700  Vara  Chain    Abcyc 

704  Vara  Chain    Abcyf 

708  Vara  Chain    Abcyg 

710  Vara  Chain     Abcyl 

715  Meter  Chain    Acbul 

719  Meter  Chain    Acfon 

723  Meter  Chain    Acily 

730  Meter  Chain    Acker 

732  Meter  Chain     Aclar 

740  Marking  Pins    Abcym 

742  Marking  Pins    Abcys 

743  Marking  Pins     Abdah 

744  Marking  Pins     Abdan 

748  Marking  Pins Abdat 

749  Marking  Pin  Carrying  Ring     Abdav 

750  Timber   Scribe    Abdax 

774  Steel  Ribbon  Chain  Tape    Abdaz 

775  Steel  Ribbon  Chain  Tape    Abdeb 

776  Steel  Ribbon  Chain  Tape Abdec 

777  Steel  Ribbon  Chain  Tape    Abdef 

778  Steel  Ribbon  Chain  Tape    Abdeg 

779  Steel  Ribbon  Chain  Tape    Abdep 

M-20  Metric  Steel  Ribbon  Chain  Tape     Abdes 

M-25  Metric  Steel  Ribbon  Chain  Tape     Anper 

M-30  Metric  Steel  Ribbon  Chain  Tape     Anrot 


322         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Cat.  No.  Description  Code  Word 

M-50  Metric  Steel  Ribbon  Chain  Tape     An  sub 

M-100  Metric  Steel  Ribbon  Chain  Tape     Antic 

V-20  Vara  Steel  Ribbon  Chain  Tape Abdew 

V-30  Vara  Steel  Ribbon  Chain  Tape    Abdid 

V-50  Vara  Steel  Ribbon  Chain  Tape     Abdik 

V-100  Vara  Steel  Ribbon  Chain  Tape    Abdin 

780  Metallic  Tape    Abdir 

782  Metallic  Tape    Abdit 

783  Metallic  Tape     Abdix 

786  Metallic  Tape    Abdob 

790  Metallic  Tape  without  Case    Abdoc 

791  Metallic  Tape  without  Case     , Abdof 

792  Metallic  Tape  without  Case     ^. . . . .  „  .  Abdog 

794  Metallic  Tape  without  Case     Abdol 

795  Reliable  Steel  Tape    Abdom 

796  Reliable  Steel  Tape    Abdop 

797  Reliable  Steel  Tape    Abdos 

798  Reliable  Steel  Tape    Abduc 

799  Reliable  Steel  Tape Abduf 

800  Reliable  Junior  Steel  Tape    Abdug 

801  Reliable  Junior  Steel  Tape    Abdul 

808  Rival  Steel  Tape    Abdum 

809  Rival  Steel  Tape Abdup 

810  Rival  Steel  Tape    Abdus 

811  Rival  Steel  Tape    Abduy 

812  Rival  Steel  Tape    Abdye 

813  Rival  Steel  Tape     Abdyk 

814  Wolverine  Steel  Tape     Abdyr 

815  "Wolverine  Steel  Tape     Abdyt 

816  Wolverine  Steel  Tape    Abdyu 

817  Wolverine  Steel  Tape    Abead 

820  Engineers  Steel  Tape     Abeah 

821  Engineers  Steel  Tape     Abeaj 

822  Engineers  Steel  Tape     Abeak 

823  Engineers  Steel  Tape     Abean 

824  Engineers  Steel  Tape    Abear 

831  Engineers  Steel  Tape    Abeat 

832  Engineers  Steel  Tape     Abeax 

833  Engineers  Steel  Tape     Abebe 

834  Engineers  Steel  Tape     Abebo 

835  Engineers  Steel  Tape    Abebu 

841  Steel  Tape  Handles    Abech 

842  Steel  Tape  Handles    Abeco 

844  Spring  Balance  for  Tapes     Abect 

846  Steel  Tape  Clamp  Handles    Abeda 


PRIVATE  CABLE  CODE  323 


Cat.  No.  Description  Code  Word 

849  String  Level    Abeds 

850  Extra  Wide  Steel  Tape    Abedy 

851  Extra  Wide  Steel  Tape Abeeb 

852  Extra  Wide  Steel  Tape    Abeec 

853  Extra  Wide  Steel  Tape    Abdiz 

854-A  Extra  Wide  Steel  Tape     Abeef 

854-B  Extra  Wide  Steel  Tape    Abeeg 

860  Pocket  Steel  Tape    Abeel 

863  Pocket  Steel  Tape    Abeem 

866  Pocket  Steel  Tape Abeep 

870  Pocket  Steel  Tape    Abees 

873  Pocket  Steel  Tape     Abefa 

875  Pocket  Steel  Tape     Abefi 

877  Pocket  Steel  Tape    Abefs 

879  Pocket  Steel  Tape    Abefy 

885  Punch  and  Riveter    Abega 

886  Extra  Eyelets     Abegi 

887  Eureka  Tape  Outfit     Abegs 

3153  Wood  Box  Pocket  Compass    Abegy 

3154  Wood  Box  Pocket  Compass    Abehe 

3155  Wood  Box  Pocket  Compass     Abeho 

3215  Brunton  Pocket  Transit     .                                                    Abeht 


324  RENSSELAER  POLYTECHNIC  INSTITUTE 

RENSSELAER  POLYTECHNIC  INSTITUTE 

TROY,  NEW  YORK 
A   School   of  Engineering  and   Science 

RECORD.  Founded  in  1824,  the  Institute  is  the 
oldest  school  of  Science  and  Engineering,  having  a  con- 
tinuous existence,  to  be  established  in  any  English 
speaking  country.  Students  have  come  to  it  from  all 
the  States  and  Territories  of  the  Union  and  from  more 
than  thirty  foreign  countries.  Its  graduates  have  be- 
come distinguished  in  the  practice  of  their  profession 
all  over  the  civilized  world. 

UNDERGRADUATE  COURSES — Courses  in  Civil,  Mechan- 
ical, Electrical  and  Chemical  Engineering  and  in  General 
Science,  each  four  years  in  duration,  leading  to  the 
degrees  Civil  Engineer  (C.  E.),  Mechanical  Engineer 
(M.  E.),  Electrical  Engineer  (E.  E.),  Chemical  Engin- 
eer (Ch.  E.),  and  Bachelor  of  Science  (B.  S.)  are  now 
given,  as  well  as  special  courses  in  Chemistry,  Water 
Analysis,  Drawing,  Surveying  Theory  and  Practice, 
Railroad  Engineering  Theory  and  Practice,  Joinery  and 
Pattern  Making,  Machine  Shop  Practice,  and  in  various 
branches  of  Theoretical  and  Applied  Engineering,  in- 
cluding work  in  the  Chemical,  Physical,  Mechanical, 
Electrical  and  Materials  Testing  Laboratories. 

GRADUATE  COURSES — Graduate  courses  leading  to 
Masters'  degrees  in  the  five  subdivisions  given  as  under- 
graduate courses  are  also  provided.  These  are  each  one 


RENSSELAER  POLYTECHNIC  INSTITUTE  325 

year  in  duration  and  lead  to  the  degrees  M.  C.  E.,  M.  M. 
E.,  M.  E.  E.,  M.  Ch.  E.,  and  M.  S.  Graduate  courses 
in  various  branches  of  science  and  engineering,  each 
three  years  in  duration,  leading  to  the  degrees  Doctor 
of  Philosophy,  Ph.  D.,  Doctor  of  Science,  Sc.  D.,  and 
Doctor  of  Engineering,  D.  Eng.,  are  also  given. 

BUILDINGS — Most  of  the  buildings  of  the  Institute 
are  situated  on  a  plot  of  ground,  containing  about 
twenty-three  and  one-half  acres,  extending  from  Eighth 
Street  eighteen  hundred  feet  easterly  to  Fifteenth  Street. 
The  Carnegie  Building,  Proudfit  Laboratory,  Walker 
Laboratory,  Russell  Sage  Laboratory,  Pittsburgh  Admin- 
istration Building  and  Library,  '87  Gymnasium,  White 
Dormitory,  Hunt  Dormitory,  Campus  Dormitory,  Rus- 
sell Sage  Dining  Hall,  Central  Heating  and  Power 
Plant,  and  Rensselaer  Union  Club  House  are  situated 
upon  it.  The  Machine  Shop  and  old  Gymnasium  are 
situated  upon  adjacent  plots.  The  Athletic  Field  is 
beside  the  Club  House  on  the  main  plot. 

APPARATUS — The  chemical,  physical,  electrical,  me- 
chanical and  testing  laboratories  are  completely  equipped 
with  the  most  modern  machines  and  apparatus.  These 
include  many  forms  of  steam  engines  and  turbines,  gas 
and  oil  engines,  pumps,  water  wheels  and  turbines,  elec- 
trical generators  and  motors,  powerful  machines  for 
testing  the  strength  of  metals,  wood,  stone,  brick,  etc., 
as  well  as  full  collections  of  apparatus  for  work  in  all 
the  laboratories  and  a  complete  assortment  of  surveying 
instruments  for  field  work. 


326  RENSSELAER  POLYTECHNIC  INSTITUTE 

INSTRUCTION — Instruction  is  given  in  the  design  and 
construction  of  roads,  railroads,  bridges,  arches,  roofs, 
water  works,  sewers,  canals,  river  improvements,  tunnels, 
foundations,  boilers,  steam  engines,  steam  turbines,  gas 
engines,  ships,  pumps,  water  wheels,  heating  and  refrig- 
erating apparatus,  electric  machinery,  dynamos  and 
telephone  and  electric  lighting  systems.  Instruction  is 
also  given  in  chemical  analysis,  electro-chemistry,  assay- 
ing, metallurgy,  mineralogy  and  geology. 

PHYSICAL  CULTURE — Lectures  on  hygiene  are  given 
and  a  large  modern  gymnasium  and  an  athletic  field, 
with  a  competent  corps  of  instructors,  provide  oppor- 
tunity for  athletic  exercise  necessary  for  the  health  of 
the  students. 

OTHER  STUDENT  ACTIVITIES — Quarters  for  the  Band, 
Glee  Club,  and  other  Musical  Clubs,  publications  and 
other  student  activities  are  provided  in  the  Club  House, 
controlled  by  a  Student  Committee. 

EXPENSES — The  tuition  for  undergraduate  courses  is 
either  $250  or  $260  a  year,  depending  upon  the  course 
taken,  and  that  for  graduate  courses  is  $150  a  year. 
Board  and  furnished  lodgings,  either  in  the  Institute 
Dining  Hall  and  Dormitories  or  in  private  houses,  may 
be  obtained  at  a  cost,  for  both,  of  from  about  $7  to  $10 
a  week.  .  /  , 

OTHER  INFORMATION — For  Catalogues  and  other 
pamphlets  giving  full  information  apply  to  the  Director 
of  Rensselaer  Polytechnic  Institute,  Troy,  N.  Y. 


TABLE  OF  CONTENTS  327 


TABLE  OF  CONTENTS 

Page 

Abney   Level  and  Clinometer 203-204 

Acoustic  Current   Meters    276,  277,  278 

Adjustable   Stadia    Wires    29 

Adjusting   or   Striding   Level 122,  123,  124 

Adjustment  of  Architects   Level    188,  189 

Engineers   Y    Level    181-187,  189-195 

Line   of  Collimation    77-79,  190-191,  256 

Objective    Slide    80-81 

Solar    Attachment    , 114-122,  139-144 

Surveyors    Compass    154-157 

Telescopic   Alidades 255,  256 

Telescopic    Sight     163-165 

Transits     76-83 

Alidades   for   Plane   Tables    246-250,  259 

Aluminum    Instruments    and    Accessories    85,  177-179 

Arc,    Vertical,   for  Transits    88 

Architects   Levels    188,  189 

Army    Sketching   Cases 260-263 

Astronomical    Terms 107-113 

Attachments  and  Extras   for   Compasses    157-163 

Levels     185 

Transits     83-106 

Ball    Spindle     151,  157 

Battery    for   Current  Meters 282 

Beaman    Stadia   Arc    29,  40,  74,  84,  90-96,  119,  248-249 

Boxes  and  Cases  for  Instruments    307,  308,  309 

Branch    Sales   Office    313 

Balance,    Precision    302,  303 

Cable    Code 315-323 

Cases    for    Instruments 58,  59,  307,  308,  309 

Centers    of    Transits 32 

Centers    of    Levels 187 

Center    Pin    , 156,  157 

Chains 268-271 

Metric  and  Vara    268,  271 

Chain    Tapes 268,  269 

Circle,    Vertical,    for  Transits    85-87 

Clamp    and    Tangent     31,  32,  41 

Clinometers     203,  204 

Collimation,    Adjustment   of   Line   of    77-79,  190,  191,  256 

Compass    Attachments    for    Levels    185 

Compass   Circle  and   Compass   Box   of   Transits    33,  34 


328         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Page 

Compasses,    Surveyors,    Attachments   and   Extras    145-180 

Compass  Attachments   for  Levels    185 

Dial     176-179 

Geologists 170-172 

Miners  Dip   Needle    173-175 

Plain    146 

Pocket    168-180 

Pocket    Vernier 180-A,  180-B 

Telescope    166,  167 

Use  of,   Adjustments  and   Repairs    152-157 

Vernier     146,  152 

Wood    Box     179,  180 

Constant    for    Stadia    Wires    70-75 

Cross    Wires     28,  29 

Cross    Wire    Reflectors    102,  103 

Meters     274-282 

Declination    Arc    114-140 

of    Magnetic    Needle    34,  35,  146 

of  the   Sun    108,  132,  134 

Tables    127-134 

Detachable  Telescopes  for  Transits    101,  102 

Diagonal  Prism  for  Eyepiece  of  Telescopes    103,  104 

Dial    Compasses    176-179 

Dip  Needle  Compasses    173-175 

Disappearing    Stadia    Wires    29 

Diurnal     Variation     149 

Dust  Guard  for  Objective  Slide  of  Telescope   26,  184 

Electric  Current   Meters    276,  278-280 

Register 281,  282 

Electricity    • 153 

Engineers    Levels     181-187 

Ephemeris,    Solar 126-314 

Explorers    Alidades    249,  250 

Levels     196,  197 

Transits,    Precise    56,  57 

Extras   for  Compasses    157-163 

for   Levels    185 

for    Transits    .-. 83-106 

Exchanging   Old   Instruments    313 

Eyepiece  for  Transit  Telescopes    26,  27 

Field  Bags  —  See  No.   498  in  Price  List. 

Figuring   of  Horizontal   Limbs    35-38 

Fixed  Stadia  Wires 28,  29 

Flagstaffs  or   Ranging  Poles    230-232 


TABLE  OF  CONTENTS  329 


Page 

Foreign    Shipments    309,  310 

Forest  Service   Compass 170-172 

Gage,   Metal  Hook   '. 283-285 

General   Information    305-314 

Geologists    Compass    170-172 

Grades,    Attachment   for   establishing 99,100 

Gradienter    96-100 

Graduations   of  Limb  and   Vertical  Circle    35-38 

Guard,    Aluminum    or    Bronze    85-87 

Guarantee 305 

Hand   Levels    202-205 

Hell  Gate  Bridge,   Erection  of    46-48 

Hook   Gage,    Metal    283-285 

Hour    Circle    and    Hour    Arc    114,  124,  141,  179 

Hydraulic   Engineering    Instruments    274-301 

Illustrations,    List   of    15-20 

Index    (Table    of    Contents)     , 327-336 

Information,    General     , 305-314 

Instructions    for    Using    Transits    .  . . , , 68,  69 

Instruments,    Selection    of    311-313 

Exchanging    Old 313 

Inverting    Eyepiece    26,  27 

Invitation   to   Visit   Factory    43,  313 

Johnson  Plane  Table  Movement    244-250 

Jointed  Leveling  and  Stadia  Rods  and  Sight  Rods 217-219,  221,  231,  232 

Latitude  Arc  115,  116 

Level 105 

Leather   Cases   and   Pouches    59 

Level  Attachments  for  Transits  35,  89,  90 

Striding  123,  124 

on  Telescope  89,  90 

Vials  and  Spirit  Levels  35,  66,  76,  77,  149,  154,  186,  191,  192 

Leveling  Adopter 157,  158 

Head 42,  52,  157,  159,  187 

Head,  3  screw  , 52 

Instruments,  Architects  188,  189 

Instruments,  Engineers  Y  181-187 

Instruments,  Explorers 196,  197 

Poles  231,  232 

Rods  and  Poles  206-232 

Screws  42 


330         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Page 

Levels,   Adjustment  of    189-201 

Attachments    for    185 

Hand    202-205 

Use    of 198-201 

Light    Mountain   Transits    54,  55 

Limbs   of   Compasses    169 

of   Transits    32,  35-38 

Line    of    Collimation     77-79,  190,  191,  256 

List   of    Illustrations    15-20 

Literature    314 

Locke    Hand    Level    202 

Magnetic  Declination    146-148 

Needle    34,  35,  146 

Magnifiers 49,  106 

Magnifying  Power  of  Telescope   27 

Marking    Pins 271 

Metallic    Tapes    269 

Meter   Chains    268 

Meters,    Current    275-282 

Miners  Dip    Needle  Compasses    , , 173-175 

Mining    Transits    44,  55,  57,  102 

Monocular  Hand  Level    204,  205 

Mountain    Transits    54,  55 

Needles     34,  66,  146-149,  154,  155 

Objective  of  Telescopes   23 

Slide   of  Telescopes    66,  185,  186,  194,  195 

Offset    Standard    161,  162 

One   Piece   Truss  Standard    30 

Optical     Axis     25,  161 

Principle    of    Telescope    23-25 

Ordering    307 

Outkeeper     149 

Packing   and   Delivery    307-309 

Parts  of  Instruments  liable  to  injury,   Prices  of  —  See  Price  List. 

Payment,    Terms  of    308 

Pins,    Marking    . . . .' 271 

Plain    Compasses     146 

Compasses,    Pocket    168,  169 

Plane    Tables    243-259 

and  Alidades,    Use  and  Adjustment  of    250-256 

Traverse    257-259 

Plates    of    Transits    32,  33 


TABLE  OF  CONTENTS  331 


Page 
Platinum    Cross   Wires 28,29 

Stadia   Wires    28,  29,  69-75 

Plumbing    Arm    243 

Plummet   Cord  —  See  Price  List. 

Lamp    104 

Plummets 272,  273 

Pocket    Compasses    168,  169 

Leveling    Rods    206-232 

Polar    Axis 122 

Poles,   Jointed  and  Ranging    231,  232 

Power   of   Telescopes 27 

Price  List  —  See  pocket  inside  of  back  cover. 

Prismatic  Eye  Piece  for  Transits  and  Telescopic  Alidades   103,  104 

Railroad    Compasses,    Pocket     168,  169 

Ranging    Poles     , 231,  232 

Reconnoissance    Transits     60,  61 

Reflectors  for  Cross  Wires  and  Limb  of  Transits    40,  102,  103 

Refractions     125,  126 

Table    of 127,  131 

Remittance    308 

Rensselaer    Polytechnic    Institute    324-326 

Repairs    to    Instruments    67,  83,  310,  311 

Riding  or  Top  Telescopes    101,  102 

Rod    Levels 233-236 

Rods  and  Poles,    Leveling,    Stadia  and   Sight 206-232 

Rods,  Flexible  or  Pocket    229 

Metric    230 

Precise     224-228 

Repairs   to    237 

Tape    , 225,  226 

Selection   of   Instruments 311-313 

Shifting  Center  for  Leveling  Head  of  Transits   42 

Short   Focus 184,  185 

Side    Telescope 101,  102 

Sketching    Cases,    Army    - 260-263 

Sketching  Case,   Fiala   Scout    264-267 

Smith  Army   Sketching   Case    : : . . . 260-263 

Sockets    of    Levels     .-.- 187 

of    Transits 41,  42 

Solar  Attachment  for  Transits    114-144 

Ephemeris     126,  314 

Screen    106 

Transits    119,  138 


332         W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 


Page 

Spirit   Levels   and   Level   Vials    35,  66,  76,  77,  149,  154,  186,  191,  192 

Stadia   Arc,   Beaman 90-96 

Constant 70-75 

Stadia    Rods 218-220 

Surveying 69-75 

Wires,    Platinum 28,  29,  69-75 

Staff    Mountings     151 

Standards    30,  31 

Steel    Tapes    269,  270 

Stop  Watch  or  Time  Recorder  for  Current  Meters  —  See  Price  List. 

Striding    Level     123,  124 

Surveyors    Chains    268 

Tables.    Declination    _ 127-134 

Plane    . , 243-259 

Tangent  Scale  on  Sight  Vanes   150 

Tape  Lines,    Metallic    269 

Lines,    Steel    269,  270 

Targets,   Special,    for  Leveling   Rods    237 

Telegraph    Codes    , 315-323 

Telescope,   How  composed    23-29 

for  Vertical  Sighting,   Detachable  or  Extra    101,  102 

Telescopic    Sight   Attachment    158-165 

Sight,    Adjustments   of    163-165 

Solar  Attachment    136,  137 

Terms  of   Payment    .'. .  -    308-310 

Three    Screw    Leveling    Head 52 

Top  or   Riding  Telescope    101,  102 

Transit    Instruments,    General    Description 23-75 

Transits,    Adjustment   of    76-144 

Care    of    62-67 

Use   of    68-75 

Attachments    for 83-144 

Distinctive  Features  of    44 

Selection    of    45 

Explorers    Precise    56-59 

Hell    Gate    49 

Light   Mountain   and   Mining    54,  55 

Precise     -. , 44-53 

Reconnoissance    60,  61 

Solar     119-138 

Solar    Attachment   for    114-144 

Transportation     307,  308 

Traverse  Plane  Table  Board  and  Tripod   257-259 

Trial    of    Instruments    .  306 


TABLE  OF  CONTENTS  333 


Page 

Tripod  Cases    242 

Tripods     43,  238-242 

Truss   Standard,    Patented,    One   Piece    30 

Use  of  Current  Meters 275,  276 

Compasses     152,  153 

Hook    Gages 284,285 

Levels    198 

Transits     68-75 

Vara  Chains  and  Tape  Lines  ; 268,  271 

Variation  Arc  of  Transits  32-34 

of  the  Magnetic  Needle  34,  35,  146-148 

Vernier  Compasses  146-152 

The  Use  of  146 

Verniers  38-40,  81 

Vertical  Arc  and  Vertical  Circle  81,  85,  86,  87,  88 

Wading  Rods  for  Current  Meters    277 

Warranty     305,  306 

Water  Stage    Registers    286-301 

Weights  of  Levels  —  See  Price  List. 
Transits  —  See  Price  List. 

Weights  and  Measures   Equipment    302-304 

Wye  Levels    181-187 

Wyes    186 

Y    Levels    181-187 

Ys  of  Leveling   Instruments    186 


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Price  List 
GURLEY  MANUAL 

Forty-Eighth  Edition 
TROY,  N.  Y.,  U.  S.  A. 

APRIL,  1921 



All  prices  in  this  list  are  in  U.  S.  Currency.     State  which  Edition 

of  Manual  when   ordering,    and  give   Catalogue  number. 

This  Price  List   supersedes   all  previous   Editions. 


TRANSITS 

Price 

Precise  Transits,  Engineers  Size,  with  one  Piece 
Truss  Standard,  6.25  in.  limb,  3Ya  in.  needle, 
11  in.  telescope,  mahogany  box  and  split  leg 
tripod. 

No.    G-A  with   clamp   and  tangent  to  telescope  axis $299.00 

No.    7-A  with   level    on    telescope    and    clamp   and   tangent 

to   telescope   axis 318.00 

No.    8-A  with  6  in.  vertical  circle,   level  on  telescope  and 

clamp    and    tangent   to    telescope    axis 346.00 

No.    9-A  with  vertical  arc  3  in.   radius,   level  on  telescope 

and  clamp  and  tangent  to  telescope  axis 346.00 

No.  10-A  with  vertical  arc  3  in.  radius,  level  on  telescope 
and  Gradienter  combined  with  clamp  and  tan- 
gent to  telescope  axis  (see  page  47) 364.00 

No.  10-A-3  like  No.  10-A,  but  with  three-screw  leveling 
head  (see  page  53) 

No.  18-A  Precise  Transit,  Hell  Gate  Model,  6.7  in.  limb, 
3%  in.  needle,  11  in.  telescope,  level  on  tele- 
scope, clamp  and  tangent  to  telescope  axis,  two 
vernier  vertical  circle  5  in.  diameter  and  level 
on  guard;  mahogany  box  and  split  leg  tripod 

(see   page  49) 575.00 

Precise  Transits,  Explorers  Size,  with  One  Piece 
Truss  Standard,  4  in.  limb,  2.13  in.  needle, 
6.5  in.  telescope,  leather  covered  mahogany 
box  and  jointed  extension  leg  tripod. 

No.  20-A  with  4  in.  vertical  circle,  level  on  telescope  and 
clamp  and  tangent  to  telescope  axis  (see  page 
57)  315.00 

No.  21-A  with  vertical  arc  2  in.   radius,   level  on  telescope 

and  clamp  and  tangent  to  telescope  axis 315.00 

No,  22-A  with  vertical  arc  2  in.  radius,  level  on  telescope 
and  Gradienter  combined  with  clamp  and  tan- 
gent to  telescope  axis 333.00 

No.  23- A  like  No.  21-A,  but  with  Burt  Solar  Attachment. .     411.00 

No.  24-A  like   No.    20-A,    but   with   a   two   vernier   vertical 

circle  baying  a  level  attached  to  the  guard...     363.00 


&•.      '.-..W.    fr.  L,   E.  GURLEY,    TROY,    NEW  YORK 
-"-» — *—*=<  •  •      "» — .  » 

•  -'*  Price 

Precise  Transits,  Light  Mountain  Size,  with 
One  Piece  Truss  Standard,  5.65  in.  limb,  3  in. 
needle,  8  in.  telescope,  mahogany  box  and  ex- 
tension leg  tripod. 

No.  25 -A  with  clamp  and  tangent  to  telescope  axis $293.00 

No.  26-A  with  level  on  telescope  and  clamp  and  tangent 

to  telescope  axis 312.00 

No.  27-A  with  4%  in.  vertical  circle,  level  on  telescope, 
clamp  and  tangent  to  telescope  axis  (see  page 
44)  :. .. : 340.00 

No.  28- A  with  vertical  arc  2.5  in.  radius,  level  on  telescope 

and  clamp  and  tangent  to  telescope  axis 340.00 

No.  29-A  with  vertical  arc  2.5  in.  radius,  level  on  telescope 
and  Gradienter  combined  with  clamp  and  tan- 
gent to  telescope  axis 358.00 

No.  30-A  like  No.  28-A,  but  with  Burt  Solar  Attachment 

(see  page  119) 436.00 

No.  32-A  like  No.  27-A,  but  with  Telescopic  Solar  Attach- 
ment (see  page  138) 515.00 

The  horizontal  limbs  of  Transits  Nos.  6-A  to 
18-A  and  Nos.  25-A  to  32-A  are  figured  in  two 
rows  0  to  360  each  way,  reading  in  opposite 
directions  and  known  as  Limb  4,  (see  page  37). 

Light  Mountain  Transits,  5.65  in.  limb,  4  in. 
needle,  8  in.  telescope,  mahogany  box  and  ex- 
tension leg  tripod. 

No.  25  with  clamp  and  tangent  to  telescope  axis 268.00 

No,  26  with  level  on  telescope  and  clamp  and  tangent 

to  telescope  axis 287.00 

No.  27  with  4%  in.  vertical  circle,  level  on  telescope 

and  clamp  and  tangent  to  telescope  axis 315.00 

No.  28  with  vertical  arc  2.5  in.  radius,  level  on  telescope 

and  clamp  and  tangent  to  telescope  axis 315.00 

No.  29  with  vertical  arc  2.5  in.  radius,  level  on  teles- 
cope and  Gradienter  combined  with  clamp  and 
tangent  to  telescope  axis 

No.    30    like  No.  28,  but  with  Burt  Solar  Attachment....     411.00 

Reconnaissance  Transits,  5  in.  limb,  3%  in- 
needle,  9  in.  telescope,  mahogany  box  and  exten- 
sion leg  tripod. 

No.  102  with  4V&  in.  vertical  circle,  level  on  telescope 
and  clamp  and  tangent  to  telescope  axis  (see 
page  61)  235.00 

No.  103     with  vertical  arc  2.5  in.  radius,  level  on  telescope 

clamp  and  tangent  to  telescope  axis 244.00 

The  horizontal  limbs  of  Transits  Nos.  20-A  to 
24-A,  Nos.  25  to  30,  and  Nos.  102  and  103,  are 
figured  0  to  90  each  way,  inner  row,  and  0  to 
360,  outer  row,  known  as  Limb  1,  (see  page  36). 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 3 

ATTACHMENTS  AND  EXTRAS 
FOR  GURLEY  TRANSITS 

The  following  prices  are  for  attachments  only  when  furnished 

with  a  new  instrument. 

When  fitted  to  a  completed  instrument,  the  cost  of  alterations 

must  he  added  to  the  price  of  the  new  parts. 

Price 

No.  131        Variation  Arc  added  to  Transits  when  sent  for 

repairs    $25.00 

No.  135-B     Vertical    Circle,    4    in.    diameter,    with    vernier 

reading    to    1    minute 18,00 

No.  136        Vertical   Circle,    4.5    in.    diameter,    with   vernier 

reading  to  1   minute    (see  page   85) 18.00 

No.  137        Vertical    Circle,    5    in.    diameter,    with    vernier 

reading  to  1  minute 22.00 

No.  138  Vertical  Circle,  5  in.  diameter,  with  two  oppo- 
site double  verniers,  reading  to  1  minute,  and 
with  guard  (see  page  86) 50.00 

No.  139  Vertical  Circle,  4.5  in.  diameter,  with  gradua- 
tions on  edge  or  rim,  protected  by  a  metal 
guard.  Circle  graduated  to  30  minutes,  with 
vernier  reading  to  1  minute  (see  page  87) . .  45.00 

No.  139-A    Vertical  Arc,  2  in.  radius,  with  vernier  reading 

to  1  minute,  movable  by  tangent  screw 28.00 

No.  139-B  Vertical  Arc,  2.5  in.  radius,  with  vernier  read- 
ing to  1  minute,  movable  by  tangent  screw. .  28.00 

No.  140  Vertical  Arc,  3  in.  radius,  with  vernier  reading 
to  1  minute,  movable  by  tangent  screw  (see 
page  88) 28.00 

No.  141        Detachable  Aluminum  Guard  for  Vertical  Circle 

(see    page    88) 9.00 

No.  145        Level  on  Telescope,  with  ground  and  graduated 

vial    (see  page   89) 19.00 

No.  146        Level    on    Telescope,    with    Reversion    Vial    (see 

page    89) 27.00 

No.  148        Clamp    and    Tangent    to    Telescope    Axis     (see 

page    89) 9.00 

No.  149  Beaman  Stadia  Arc,  for  Transit  having  a  one- 
vernier  vertical  circle  or  vertical  arc  (see 
page  40) 22.00 

No.  149-A  Beaman  Stadia  Arc,  for  Transit  having  a  two- 
vernier  vertical  circle  No.  138 50.00 

No.  149-B    Beaman  Stadia  Arc,  for  Telescopic  Alidades  Nos. 

592  and  592-A 20.00 

No.  149-C    Beaman  Stadia  Arc  with   edge   graduations,   for 

Telescopic  Alidade   No.    584-B 45.00 

No.  150        Gradienter,   combined   with  Clamp  and  Tangent 

(sea  page  96) 27.00 

No.  151  Platinum  Stadia  Wires,  adjustable,  and  dia- 
phragm    8.00 

No.  152        Platinum    Stadia    Wires,    fixed,    and    diaphragm      10.00 

No.  154        Dust  Guard  to  objective  slide   (see  page  26) ...         7.00 

No.  155        Pinion  movement  to  eyepiece  slide 8.00 

No.  157        Sights    on    Telescope,    with   folding    joints 12.00 

No.  158  Sights  on  Standards,  at  right  angles  with  teles- 
cope    12.00 

No,  160        Detachable  Side  Telescope  and  Counterpoise,  for 

vertical  sighting    (see  page  101) 40.00 

No.  161  Detachable  Riding  Telescope,  for  vertical  sight- 
ing (see  page  101) 40.00 


4  W.    &  L.    E.    GUBLEY.    TROY.    NEW   YORK 

Price 
No.  165        Reflector  for  illuminating  cross  wires   (see  page 

103)     $12.00 

No.  166        Reflector  for   illuminating   cross   wires   of   large 

Wye  Level   (see  page  103) 15.00 

The    elliptical    reflecting    pieces    on    Reflectors 

Nos.  165  and  166  are  of  sterling  silver. 
No.  167        Elbow  Eyepiece,  in  addition  to  regular  eyepiece, 

and     interchangeable 50.00 

No.  168        Diagonal   Prism   for   eyepiece    of  telescope    (see 

page    103) 12.00 

No.  169        Eyepiece    Cap   with   darkener   glass    in   shutter, 

for    direct    solar    observations 3.00 

No.  170        Plummet    Lamp    for    mine    surveying    (see   page 

104)     15.00 

No.  180        Attached  Magnifier,  with  three  universal  joints, 

to  read  verniers   (see  page   106)    each 8.00 

No.  181  Attached  Microscopes  to  read  verniers  of  hori- 
zontal limb,  as  shown  with  No.  18-A  Transit 
(see  page  106)  per  pair 30.00 

No.  182  Attached  Microscopes  to  read  verniers  of  No. 
138  vertical  limb,  as  shown  with  No.  18-A 
Transit  (see  page  106)  per  pair 30.00 

No.  185        Graduation  of  horizontal  limb  to  read  to  20  or 

30    seconds,    extra 15.00 

No.  186        Graduation    of    horizontal    limb    to    read    to    10 

seconds,    extra 35.00 

No.  187        Graduation    of   4.5    or   5    in.    Vertical    Circle    to 

read  to  20  or  30  seconds,   extra 10.00 

No.  188        Graduation  of   No.    138   Vertical   Circle   to   read 

to   20  or  30   seconds,    extra 15.00 

No.  189        Graduation   of   No.    138   Vertical   Circle   to  read 

to    10    seconds 35.00 

No.  190  Burt  Solar  Attachment,  with  declination  arc, 
hour  circle,  polar  axis,  patent  latitude  level, 
adjusting  level  and  adjusting  bar  (see  page 
115)  96.00 

No.  192        Solar   Screen,    to   fit   eyepiece   of   telescope    (see 

page    106) 12.00 

No.  193        Patent  Latitude  Level,   for  use  with  Burt  Solar 

Transit     9.00 

No.  196        Striding    or   Adjusting   Level 8.00 

No.  197        Adjusting  Bar  for  Solar  Attachment  of  Transit        2.25 
For    prices    of   Parts    of   Instruments    Liable   to 
Loss  or  Injury,    see  pages  21   to  25. 

SURVEYORS  COMPASSES 

Vernier    Compass 

Price  Postage 

No.  226  5  in.  needle,  brass  cover,  outkeeper,  mahog- 
any box  and  Jacob  staff  mountings  (see 
page  150)  $65.00 

Attachments   and    Extras   for 
No.   226    Compass 

No.  241        Leveling    Adopter    (see    page    158) 10.00     .40 

No.  242  Leveling  Head,  with  four  leveling  screws 
and  clamp  and  tangent  fitted  to  use  with 
Tripods  Nos.  415,  420  and  425  (for  Tripods 
see  page  238) 25.00 


W.    &   L.    E.    GURLEY,    TROY,    NEW   YORK 


Price  Postage 

No,  262  Achromatic  Telescope,  9  in.,  aperture  of 
objective  0.69  in.,  power  about  20  diam., 
•with  platinum  cross  wires  and  stadia 
wires,  level,  clamp  and  tangent  and  3  in. 
vertical  circle,  reading  by  vernier  to  6 

min.,    (see   page   160) $63.00     .60 

No,  268  Offset  Standard  with  counterpoise,  to  bring 
the  telescope  over  the  line  of  zeros  (see 
page  162) 10.00 

Pocket  Compass  with  Limb 

No.  286  6  in.  limb,  with  one  vernier  reading  to  one 
minute,  3%  in.  needle,  folding  sights,  two 
levels,  mahogany  box,  Jacob  staff  mount- 
ings and  tripod  (see  page  168) 76.00 

Or    with   Extension    leg    tripod 80.00 

Compass  with  Limb  and  Telescope 

No.  294  4  in.  limb,  with  one  vernier  reading  to  one 
minute,  4%  in.  needle,  6.6  in.  telescope, 
level  on  telescope,  clamp  and  tangent  to 
telescope  axis,  4  in.  vertical  circle  with 
vernier  to  one  minute,  leveling  head,  ma- 
hogany box  and  solid  round  leg  tripod 

(see   page   167) 150.00 

Or  with  Extension  leg  tripod 166.00 

Pocket  Vernier  Compass 

No.  300  3%  in.  needle,  folding  sights,  two  levels, 
mahogany  box  and  Jacob  staff  mountings 
(see  page  180-A) 28.00  .70 

No.  305  4ya  in.  needle,  folding  sights,  two  levels, 
mahogany  box  and  Jacob  staff  mountings 
(see  page  180-A) 33.00  1.00 

No.  491        Leather   Pouch   for    No.    300 5.75     .20 

No.  492        Leather   Pouch    for   No.    305 7.00    .26 

ATTACHMENTS  AND  EXTRAS 
FOR  POCKET  COMPASSES 

No.  325  Clamp  and  Tangent  to  ball  spindle  of  Com- 
passes Nos.  285,  300  and  305 6.00 

No.  326  Rack  and  Pinion  to  variation  arc  of  Com- 
passes Nos.  300  and  305 6.00 

No.  327  Leveling  Adopter  for  Compasses  Nos.  285, 

300  and  305 7.50  .26 

Geologists   Compass    (Aluminum) 

No.  335  United  States  Forest  Service  pattern,  2% 
in.  needle,  graduated  movable  sighting 
circle,  graduated  base,  variation  arc,  fold- 
ing sights,  two  levels,  clinometer,  mahog- 
any box  and  Jacob  staff  mountings  (see 
page  171) 36.00  .85 

No.  490        Leather   Pouch   for    No.    336 6.00    .20 


6  W.    &  L.    E.    GURLEY,    TROY,    NEW   YOEK 

Miners   Compasses   or  Dip    Needles 

For  prospecting  for  magnetic  iron  ore 

Price  Postage 
No,  341  3  in.  needle  with  stop,  glass  on  both  sides 

and  brass  covers  (see  page  174) $20.00  .35 

No.  341-A  3  in.  needle  with  stop,  glass  on  both  sides, 

brass  covers  and  attached  level 23.00  .35 

No.  490  Sole  Leather  Pouch  with  belt  loop  for  Nos. 

341   and  341-A 5.00     .20 

Dial    Compass    (Aluminum) 

No.  350  2%  in.  needle  with  hour  circle  graduated 
for  any  latitude  between  20  and  50  de- 
grees, as  ordered;  graduated  base,  grad- 
uated movable  sighting  circle,  variation 
arc,  one  folding  sight,  one  removable  sight, 
two  levels,  clinometer,  mahogany  box  and 

Jacob    staff    mountings 40.00     .45 

Special  Sight  for  latitude  above  50   degrees     12.00 
Extra  Hour  Circles   graduated  for  any  lati- 
tude   between    20    and    50    degrees    to    fit 
Dial    Compass,     each 6,00     .14 

No.  490        Sole  Leather  Pouch    (see  page  176) 5.00     .20 

Wood  Box  Pocket   Compasses 

No.  3153  Mahogany  case,  3%  in.  square  by  1%  in. 
deep,  needle  circle  graduated  on  raised 
ring  to  whole  degrees,  figured  0  to  90 
each  way,  needle  2  in.  long  with  jeweled 
center  and  automatic  stop,  hinged  cover 
with  clasp,  weight  4  oz 4.00  .15 

No.  3154      Like  No.  3153,  but  with  needle  circle  figured 

0  to  360  (see  page  180) 4.00     .15 

No.  3155      Like    No.    3153,    but   3%    in.    square   by   1% 

in.  deep,  needle  2%  in.  long,  needle  circle 

figured   0   to   90   each   way,    weight   5    oz.       5.00     .20 

Piano  Hinge,  full  width  of  cover,  instead  of 

two    small   hinges   on   Nos.    3153,    3154   or 

3155,    extra 1.00 

Township    Diagram    on    inside    of    cover  of 
Nos.  3153,  3154  or  3155,  extra 1.00 

LEVELING  INSTRUMENTS 
Engineers  Wye  Levels 

No.  375        22    in.    telescope,    power    42    diam 225.00 

No.  377        18    in.    telescope,    power    32    diam 215.00 

No.  378        15    in.    telescope,    power    26    diam 205.00 

All  of  the   above  Levels   are   equipped  with 
mahogany  box  and  split  leg  tripod. 


W.    &   L.    E.    GTTRLEY,    TROY,    NEW   YORK 7 

Attachments  and  Modifications  for 

Engineers  Wye  Levels 
Not.  375,  377  and  378,  when  ordered  with 

the  instruments  can  be  supplied  as  follows: 

Price 
Stadia  Wires  of  platinum,  adjustable,  disappearing  or 

fixed No  extra  charge 

Morocco  Finish,  on  telescope  and  level  tube No  extra  charge 

Level  Vial,  extra  sensitive,  value  ten  seconds  to  one-tenth 

of  an  inch  (instead  of  regular  vial),  extra $10.00 

Pinion  Movement  to  objective  slide,  for  Level  No.  378, 

extra  8.00 

Dust  Guard  to  objective  slide,  for  Level  No.  378,  extra...  8.00 
Horizontal  Limb,  full  circle,  3.5  in.  diameter,  graduated 

to  degrees,  reading  by  vernier  to  5  minutes,  as  shown 

on  page  185,  extra 25.00 

Compass,  with  needle  circle  graduated  to  degrees,  needle 

3   in.    long,    with    stop.     Attached   on   top   of   telescope 

and  secured  with  two  clamp  screws,  as  shown  on  page 

185,  extra 25.00 

Mirror,  for  observing  level  bubble  from  eyepiece  end  of 

instrument,  as  shown  on  page  185,  extra 15.00 

Reflector  No.  166,  for  illuminating  cross  wires.  Similar 

to  No.  165,  (see  page  103) 15.00 

Waterproof  Hood,  extra 1.25 

Extension  Leg  Tripod  No.  440,  inst«ad  of  split  leg  tripod, 

extra  3.00 

Sole  Leather  Carrying  Case,  to  enclose  mahogany  box,  22.00  to  26.00 

Sole  Leather  Case,  for  extension  tripod,  extra 25.00 

Canvas  Case  with  leather  mountings,  for  extension  tripod, 

extra  15.00 

Special  Outside  Packing  Box  with  hinged  cover  and  lock, 

lined   inside  with   rubber   cushions,    for   convenience   in 

reshipping,    extra 8.00 

Architects  Wye  Level 

No.  381        12  in.   telescope,  mahogany  box  and  solid  round 

leg    tripod    125.00 

Attachments  and  Extras  for  No.  381  Level 
When  Ordered  with  the  Instrument 

Stadia    wires    of    Platinum,     adjustable,     disappearing    or 

fixed No  extra  charge 

Pinion  Movement  to  eyepiece 8.00 

Dust  Guard  to  objective  slide 8.00 

Compass,  with  full  needle  circle  graduated  to  whole  degrees, 
figured  0  to  90  each  way,  needle  3  in.  long,  with  stop. 
Attached  on  top  of  telescope  and  secured  with  two 
clamp  screws  25. 00 


W.    &  L.    E.    CKTRLEY,    TROY. 


Price 
Waterproof  Hood   ........................................       $1.25 

Split  Leg  Tripod  No.  436,  instead  of  solid  round  leg  tripod  3.00 
Extension  Leg  Tripod  No.  441,  instead  of  solid  round  leg 

tripod    ...............................................         8.00 

Explorers   Level 

No.  384        6.5  in.  telescope,  leather  covered  mahogany  box 

and  jointed  extension  leg  tripod  (see  page  197)     120.00 

HAND  LEVELS 

No.  643        Locke  Level,  Gurley  make  (see  page  202)  ......  9.25 

Or  Locke  Level,  Taylor  make  ..................  7.50 

No.  646        Abney   Level    (see  page   203)  ..................  15.50 

No.  640        Monocular  Level    (see  page  204)  ...............  20.00 

TRIPODS 

Instructions  for   Ordering  Tripods 

The  majority  of  the  Nos.  400  to  443  include  more  than  one 
size  tripod.  For  instance,  No.  400  covers  two  sizes;  one  size  for 
Transits  Nos.  6-A  to  18-A.  and  another  size  for  Transits  Nos.  25-A 
to  32-A  and  Nos.  25  to  30. 

Therefore,  when  ordering  a  separate  tripod,  the  customer 
should  always  specify  the  catalogue  number  of  the  instrument  for 
which  it  is  intended;  also  give  the  inside  diameter  of  the  bottom 
plate  of  the  leveling  head.  If  the  instrument  is  very  old,  it  will 
be  necessary  to  send  us  the  bottom  plate  of  the  leveling  head. 

Transit    Tripods 

No.  400        Solid  Round  Leg  Tripod,   for  Transits  Nos.   6-A 

to  32-A   (except  Nos.   20-A  to  24-A)  .........     $15.00 

No.  401  Solid  Round  Leg  Tripod,  for  Transits  Nos.  20-A 

to  24-A  and  Nos.   102  and  103..  .............       12.00 

No.  405  Split  Leg  Tripod,  for  Transits  Nos.  6-A  to  32-A 

(except   Nos.    20-A   to   24-A)  .................       20.00 

No.  406  Split  Leg  Tripod,  for  Transits  Nos.  20-A  to  24-A 

and   Nos.   102   and   103  .......................       15.00 

No.  410  Extension  Leg  Tripod,  for  Transits  Nos.  6-A  to 

32-A    (except  Nos.   20-A  to  24-A)  ............       23.00 

No.  411  Extension  Leg  Tripod,  for  Transits  Nos.  20-A  to 

24-A  and  Nos.   102  and  103  ..................       20.00 

No.  412  Jointed  Extension  Leg  Tripod,  with  canvas  case, 

for    Transits   Nos.    20-A   to   24-A  .............       25.00 

Compass  Tripods 

No.  415  Solid  Round  Leg  Tripod,  for  Compass  No.  226..  10.00 
No.  416  Solid  Round  Leg  Tripod,  for  Compasses  Nos. 

285,    294.    300,    305,    335    and    350  ............  9.00 

No.  420        Split  Leg  Tripod,  for  Compass  No.  226  .........  15.00 

No.  421  Split  Leg  Tripod,  for  Compasses  Nos.  285,  294, 

300,  305,  335  and  350  ........................  12.00 

No.  425  Extension  Leg  Tripod,  for  Compass  No.  226...  20.00 
No.  426  Extension  Leg  Tripod,  for  Compasses  Nos.  285, 

294,   300,    305,    335   and   350  ..................  15.00 


W.    &   L.    E.    GURLEY,    TROY,    NEW   YORK 


Level  Tripods 


No.  430  Solid  Round  Leg  Tripod,  for  Levels  Nos.  375 
to  378  ..................................... 

No.  431        Solid  Round  Leg  Tripod,   for  Level   No.   381... 

No.  435        Split  Leg  Tripod,   for  Levels  Nos.   375  to  378.  . 

No.  436        Split  Leg   Tripod,    for  Level   No.    381  .......... 

No.  440        Extension  Leg  Tripod,  for  Levels  Nos.  375  to  378 

No.  441        Extension  Leg  Tripod,   for  Level  No.   381  ...... 

No.  443  Jointed  Extension  Leg  Tripod,  with  canvas  case, 
for  Level  No.  384... 


Price 

$15.00 
12.00 


15.00 
23.00 
20.00 

25.00 


No.  494 
No.  496 
No.  497 


Carrying  Cases  for  Tripods 

To  protect  the  tripod  in  transportation,  a 
carrying  case  can  be  furnished.  One  style  of 
case  is  substantially  made  of  heavy  canvas,  with 
leather  trimmings.  Another  form  is  made  of 
sole  leather,  with  cap  and  carrying  handle. 

Leather  Case,  with  cap  and  carrying  handle, 
for  extension  tripod 

Canvas  Case,  with  leather  trimmings,  for  solid 
round  leg,  or  split  leg  tripod 

Canvas  Case,  with  leather  trimmings,  for  ex- 
tension tripod  


25.00 
18.00 
15.00 


PLUMMETS 
Brass  Plummets  —  Plain 


No.  450  Plummet,  screw  head,  steel  point,    6  oz. 

No.  452  Plummet,  screw  head,  steel  point,  10  oz. 

No.  454  Plummet,  screw  head,  steel  point,  16  oz. 

No.  456  Plummet,  screw  head,  steel  point,  24  oz. 

No.  458  Plummet,  screw  head,  steel  point,  32  oz. 

No.  460  Plummet,  screw  head,  steel  point,  long    neck 

12  oz 


Price  Postage 
$1.50  .15 
2.00  .20 
3.00  .25 
3.50  .35 
4.00  .45 


2.50     .25 


Brass  Plummets  —  Adjustable 

This  Plummet  has  a  concealed  reel,  R, 
around  which  the  string  is  wound  by  turning 
the  milled  head,  K,  on  top.  The  friction 
upon  the  reel  will  hold  the  Plummet  at  any 
desired  point  of  the  line. 

No.  465        Adjustable  Plummet,  10  oz 5.00    .20 


Spads,  Stake  Tacks,  Plummet  Cord 

No.  471        Iron    Spads,    for    suspending    plummets    in 

mines,    per    100 2.00  .15 

No.  472        Stake  Tacks,   galvanized,    2  oz,    box .10  .04 

No.  473        Stake   Tacks,   galvanized,    1  Ib.    box 55  .20 

No.  474        Plummet  Cord,   braided  linen,   per  25  yards        .38  .04 


10  W.    &   L.    E.    GTTRLEY,    TROY,    NEW    YORK 


LEATHER  CASES  AND  POUCHES 

Sole    Leather    Cases,    with    Shoulder    Straps 
to   fit   outside   the   wooden   box, 

Price  Postage 

No.  475         Case  for  Precise  Transits  Nos.  6-A  to  18-A. .  $25.00 
No.  476         Case  for  Light  Mountain  and  Reconnoissance 

Transits   Nos.    25-A  to  30;   102   and   103..     22.00 
No.  476-A     Leather  covered  mahogany  box  for  Explorers 

Precise   Transits   Nos.    20-A   to   24-A 20.00 

No.  478        Case    for    Compass    No.    226 17.50 


No.  479         Case   for   Engineers   Wye    Levels;    No.  375. 

No.  377. 

No.  378. 
No.  480        Case   for   Architects   Wye  Level   No.    381. 


26.00 
24.00 


14.50 


No.  481         Case    for    Telescopic    Alidades    Nos.     584-B 

or  584-C    24.00 

No.  482        Leather  covered  mahogany  box  for  Explorers 

Telescopic    Alidade    No.    592-C 20.00 

No.  485         Case  for  Compasses   Nos.    335    and   850 6.00     .22 

No.  486        Case  for  Compass   No.    300 6.50     .32 

No.  487        Case  for  Compasses    Nos.    285    and    305 7.50     .50 

Sole  Leather  Pouches,   with  Shoulder  Straps 
Fitted  to  receive  Pocket  Compasses  with- 
out  wooden   box. 
No.  490        Pouch  for  Compasses    Nos.     335,    341,    341-A 

and     350     5.00     .18 

No.  491         Pouch  for  Compass    No.     300 5.75     .28 

No.  492        Pouch  for  Compass    No.    305 7.00     .38 

Tripod   Cases 

No.  494  Leather  Case  with  cap  and  carrying  handle 

for  extension  leg  tripod 25.00 

No.  496  Canvas  Case  with  leather  trimmings  for 

solid  round  leg  or  split  leg  tripod 18.00 

No.  497  Canvas  Case  with  leather  trimmings  for 

extension  leg  tripod 15.00 

Engineers   Leather   Field  Bag 

No.  498  Heavy  sole  leather  with  two  extra  pockets, 
with  shoulder  strap,  inside  measure  9  in. 
long,  7  in.  high,  2%  in.  wide 8.00  .35 

LEVELING  RODS,  STADIA  RODS 
AND  SIGHT  RODS 

No.  500  Philadelphia  Rod,  2  ply,  7-3/10  ft.  closed, 
sliding  to  13  ft.,  graduated  to  feet,  lOths 
and  lOOths,  with  verniers  reading  to 
lOOOths,  and  with  Micrometer  target  (see 
page  210)  22.50 

No.  500- A    Philadelphia  Rod,   2   ply,    6-8/10   ft.    closed, 

sliding  to  12  ft.,  graduated  to  feet,   lOths 

and     lOOths,     with     verniers     reading     to 

lOOOths,    and    with    Micrometer    target...     22.50 

Either  of  the  above  Rods  with  Plain  target 

(no    micrometer)     20.00 


W.    &   L.    E.    GURLEY,    TROY,    NEW   YORK 


11 


Price 

No.  500-R  Service  Rod,  self -reading,  2  ply,  7-3/10  ft. 
closed,  sliding  to  13  ft.,  graduated  to  feet, 
10th  and  lOOths,  with  verniers  reading  to 
lOOOths  and  with  oval  target  (see  page  211)  $15.00 

No.  500-B  Philadelphia  Rod,  2  ply,  7-3/10  ft.  closed, 
sliding  to  13  ft.,  graduated  to  feet,  lOths 
and  half  lOths,  with  both  target  and  rod 
reading  to  natural  scales  to  lOOths;  the 
lOths  figures  are  0.06  ft.  high  (see  page 
212)  20.00 

No.  501  Philadelphia  Rod,  3  ply,  5-3/10  ft.,  closed, 
sliding  to  13  ft.,  graduated  to  feet,  lOths 
and  lOOths,  with  verniers  reading  to 

lOOOths    (see   page   213) 27.50 

Nos.     500-B     and    501    have    plain    targets. 

If   with   Micrometer   target,    add 2.50 

If   with   Angle   target,    add 2.60 

If   with   Micrometer   Angle   target,    add 3.50 

No.  501-B  Special  Self-reading  Rod,  3  ply,  7-6/10  ft. 
closed,  sliding  to  20  ft.,  graduated  on  four 
faces  to  feet  and  lOths,  and  on  back  of 
the  front  section  to  feet,  lOths  and  lOOths; 
also  reading  by  two  scales  to  half- 
hundredths.  With  aluminum  target  and 
canvas  case  (see  page  214) 31.25 

No.  502-A  Philadelphia  Mining  Rod,  2  ply,  3-3/10  ft. 
closed,  sliding  to  5  ft.,  graduated  to  feet, 
lOthg  and  lOOths,  with  vernier  reading  to 

lOOOths    18.00 

Canvas    Cases    for    Rods    Nos.    500,    500-A, 
500-R,  500-B  and  501 4.50 

No.  505  New  York  Rod,  2  ply,  6-8/10  ft.  closed, 
sliding  to  12  ft.,  graduated  to  feet,  lOths 
and  lOOths,  with  vernier  reading  to 
lOOOths  (see  page  215) 20.00 

No.  510  Architects  Rod,  2  ply,  5%  ft.  closed,  slid- 
ing to  10  ft.,  graduated  to  feet,  inches 
and  16ths  (see  page  216) 10.00 

No.  511  Architects  Rod,  2  ply,  5%  ft.  closed,  slid- 
ing to  10  ft.,  graduated  to  feet,  lOths 
and  lOOths,  with  verniers  reading  to 
lOOOths  10.00 

No.  513  Telemeter  or  Stadia  Rod,  without  target, 
hinge  joint,  6  ft.  folded,  unfolding  to  12 
ft.,  graduated  to  feet,  lOths  and  lOOths 
(see  page  220) 15.00 

No.  514  Telemeter  or  Stadia  Rod,  without  target, 
hinge  joint,  7  ft.  folded,  unfolding  to  14 
ft.,  graduated  to  feet,  lOths  and  lOOths. .  16.00 

No.  514-B  Stadia  Rod,  one  piece,  without  target,  10 
ft.  long,  4  in.  wide,  with  brass  ends, 
graduated  on  recessed  face  of  3%  in. 
width  to  feet,  lOths  and  2/100ths  (see 
page  218)  12.50 

No.  514-C    Stadia   Rod,    similar   to    No.    514-B,    but   12 

ft.    long    15.00 


12 


W.    &   L.    E.    GTTRLEY,    TROY,    NEW   YORK 


The  graduations  of  Nos.  514-B  and  514-C 
begin  at  the  base  and  end  at  the  top  of 
the  rods.  The  illustration  on  page  218 
does  not  show  completed  graduations. 

No.  514-D  Stadia  Rod,  one  piece,  without  target,  10 
ft.  long,  3l/s  in.  wide,  with  brass  ends, 
graduated  on  flat  face  to  feet,  lOths 
and  2/100ths  (see  page  218) 

No.  514-E  Stadia  Rod,  similar  to  No.  514-D,  but  12 

feet  long  

Hinge  Joint  for  Stadia  Rods  Nos,  514-B, 
514-C,  514-D  or  514-E,  to  permit  folding, 

extra  

Rods  Nos.  513  to  514-E  can  be  furnished  in 
any  length  up  to  16  ft.  Prices  on  appli- 
cation. 

No.  515  Telescopic  Rod,  3  ply,  without  target,  5  ft. 
closed,  sliding  to  14  ft.,  graduated  to 
feet,  lOths  and  lOOths 

No.  516  Cross  Section  Rod,  one  piece,  without  target, 
10  ft.  long,  with  level  at  each  end,  grad- 
uated to  feet,  lOths  and  lOOths  (see 
page  221)  

No.  517  Slip- Jointed  Leveling  or  Stadia  Rod,  12  ft. 
long,  two  inch  graduated,  recessed  face, 
three  sections  (two  slip  joints),  graduated 
in  feet,  lOths  and  lOOths.  The  joints  are 
secured  and  released  by  spring  catches. 
(See  page  217).  With  canvas  carrying  case 

No.  518-A  Plain  Rod,  one  piece,  without  target,  10  ft. 
long,  graduated  to  feet,  lOths  and  lOOths 
(see  page  221) 

No.  518-B  Plain  Rod,  without  target,  hinge  joint,  5 
ft.  folded,  unfolding  to  10  ft.,  graduated 
to  feet,  lOths  and  lOOths 

No.  519-A  Plain  Rod,  one  piece,  without  target,  12  ft. 
long,  graduated  to  feet,  lOths  and  lOOths 

No.  519-B     Plain  Rod,  without  target,  with  hinge  joint, 

6  ft.    folded,    unfolding    to    12    ft.,    grad- 
uated to   feet,   lOths   and   lOOths 

No.  520-A    Plain  Rod,  one  piece,  without  target,  14  ft. 

long,   graduated  to  feet,   lOths  and  lOOths 

No.  520-B     Plain  Rod,  without  target,  with  hinge  joint, 

7  ft.    folded,    unfolding    to    14   ft.,    grad- 
uated to  feet,  lOths  and  lOOths 

No.  521-B     Plain  Rod,  without  target,  with  hinge  joint, 

8  ft.    folded,    unfolding    to    16    ft.,    grad- 
uated to   feet,    lOths   and   lOOths 

No.  522-A  Plain  Rod,  2  ply,  without  target,  5-3/10  ft. 
long,  sliding  to  10  ft.,  graduated  to  feet, 
lOths  and  lOOths 

No.  522-B  Plain  Rod,  2  ply,  without  target,  6-3/10  ft. 
long,  sliding  to  12  ft.,  graduated  to  feet, 
lOths  and  lOOths 

No.  522-C  Plain  Rod,  2  ply,  without  target,  7-3/10  ft. 
long,  sliding  to  14  ft.,  graduated  to  feet, 
lOths  and  lOOths... 


Price 


10.50 
5.00 

25.00 
17.50 

17.00 
7.50 

11.25 
8.75 

13.75 
10.00 

15.00 
16.25 
11.25 
12.50 
13.75 


W.    &   L.    E.    GURLEY,    TROY,    NEW   YORK 


13 


Price  Postage 
No.  524-A    Plain  Rod,  4  ply,  without  target,  3-3/10  ft. 

long,   sliding  to  11-2/10  ft.,  graduated  to 

feet,   lOths  and  lOOths   (see  page  223)...  $17.50 

Canvas   Case   for   No.    524-A 3.00 

No.  525-B    Pocket  Rod,  10  ft.  long,  graduated  to  feet, 

lOths  and   lOOtlis    (see  page   229) 4.50    .25 

No.  526-A    Pocket  Rod,  12  ft.  long,  graduated  to  feet, 

lOths    and    lOOths 5.50     .28 

No.  526-B    Pocket  Rod,  12  ft.  long,  graduated  to  feet, 

inches    and    8th 5.50    .28 

No.  527        Pocket  Rod,   14  ft.  long,  graduated  to  feet, 

lOths  and  lOOths 7.00    .30 

No.  528        Pocket  Rod,  3%   meters  long,   graduated  to 

centimeters    5.50    .30 

No.  530        Wooden   Leveling   Pole   and  Flagstaff,    7  ft. 

long    6.25 

No.  531        Wooden  Leveling  Pole  and  Flagstaff,   9   ft. 

long    7.50 

No.  534  Wooden  Flagstaff,  octagonal,  6  ft.  long...  3.50 
No.  535  Wooden  Flagstaff,  octagonal,  8  ft,  long1. . .  4.25 
No.  536  Wooden  Flagstaff,  octagonal,  10  ft.  long...  5.25 

(see  page  230). 
No.  537-A    Jointed  Wooden  Flagstaff,  round,  6  ft.  long, 

in    2    sections 5.50 

No.  537-B    Jointed  Wooden  Flagstaff,  round,  6  ft.  long, 

in  2  sections  and  with  canvas  case 8.75 

No.  537-C    Jointed  Wooden  Flagstaff,  round,  6  ft.  long, 

in    3    sections 8.75 

No.  537-D    Jointed  Wooden  Flagstaff,  round,  6  ft.  long, 

in  3  sections  and  with  canvas  case 12.00 

No.  538-A    Jointed  Wooden  Flagstaff,  round,  9  ft.  long, 

in    3    sections 9.50 

No.  538-B    Jointed  Wooden  Flagstaff,  round,  9  ft.  long, 

in  3  sections  and  with  canvas  case 13.00 

(see  page  232). 
No.  540-A    Steel  Ranging  Pole,   solid,   hexagonal,   6  ft. 

long,    ya   in.    diameter 4.00 

No.  540-B     Steel  Ranging  Pole,   solid,   hexagonal,   8  ft. 

long,    %    in.    diameter 4.76 

No.  541        Iron    Tubular    Ranging    Pole,      6    ft.    long, 

13/16    in.    diameter 3.75 

No.  543        Iron    Tubular    Ranging    Pole,      8    ft.    long, 

13/16    in.    diameter 4.50 

No.  544        Iron    Tubular    Ranging    Pole,    10    ft.    long, 

13/16    in.    diameter 5.00 

(see  page  231). 
No.  550-R     Gurley    Precise    Leveling    Rod,     cross-shape 

section,  graduated  on  three  faces  to  yards, 

lOths   and   lOOths,    reading   to   3ya    yards, 

with  silver-faced  plugs  at  each  half  yard. 

Fitted  with  wooden  handle,   thermometer, 

fixed     circular    rod    level,     canvas     case, 

turning   point   and   plate.       Packed   in    a 

special  pine  box  with  hinged  cover,  han- 
dles and  lock   (see  page  227) 110.00 


14 W.    &  L.    E.    GTJRLEY,    TEOY,    NEW   YOEK 

Price 

No.  551-R  Molitor  Precise  Leveling  Rod,  T-shape  sec- 
tion, 12  ft.  long,  graduated  to  feet,  lOths 
and  lOOths,  or  to  millimeters  if  pre- 
ferred, and  with  circular  level,  two  wooden 
handles,  plumbing  attachment  and  plum- 
met, enclosed  thermometer,  canvas  case, 
and  turning  point.  Packed  in  special  pine 
box  with  hinged  cover,  handles  and  lock 

(see    page    224) $85.00 

No.  552-R     Self -Reading  Tape  Leveling  Rod;  rod  made 

of  pine,  10  ft.  Bl/z  in.  long,  and  graduated 

on  one  edge  to  feet  and  lOths.     The  steel 

•  ribbon     graduated     to     feet,      lOths     and 

half-lOths;     all    graduations    on    rod    and 

tape    are    painted    (see    page    225) 47.50 

Canvas   Case   for  above   rod 5.00 

ROD  LEVELS 

No.  545  (See  page  233) 5.00 

No.  546  (See   page  234) 6.00 

No.  547  (See*  page  235) 10.00 

No.  548  (See   page  236) 13.00 

PLANE  TABLES 
Plane  Tables,  Equipment  and  Parts 

(See  pages  243  to  259) 

No.  570        Johnson    Plane    Table    Movement    and    split 

leg   tripod    , 45.00 

No.  570-A  Johnson  Plane  Table  Movement  and  exten- 
sion leg  tripod 57.00 

No.  571  Johnson  Plane  Table  Movement,  special 
light  weight  model,  with  special  light 
weight  extension  leg  tripod 50.00 

Canvas  Case,   leather  trimmed,   for  No.    571      9.00 
No.  573        Drawing    Board,    31    x    24    in.,    with    brass 
screw  plate  fitted,    and  with   eight   clamp 
screws  and  sockets  for  paper 9.00 

Canvas-covered  Wooden  Case  for  No.    573..       8.00 

Flexible    Canvas    Case   with    shoulder    strap, 

for    No.    573 4.75 

Eggshell  Drawing  paper,  single  mounted, 
31  x  24  in.,  per  sheet 1.25 

Eggshell  Drawing  Paper,  double  mounted 
(muslin  between),  so  that  drawings  can 
be  made  on  both  sides,  31  x  24  in.,  per 

sheet    2.50 

No.  573-A  Drawing  Board,  18  x  24  in.,  with  brass 
screw  plate  fitted,  and  eight  clamp  screws 
and  sockets  for  paper 8.00 

Canvas-covered  Wooden  Case  for  No.   573-A      6.25 

Flexible    Canvas    Case   with    shoulder    strap, 

for  No.  573-A 3.00 

Eggshell  Drawing  paper,  single  mounted, 
18  x  24  in.,  per  sheet 85 


W.    &   L.    E.    GTTRLEY,    TROYJEW   YORK  16 

Price 

Eggshell  Drawing  Paper,  double  mounted 
(muslin  between),  so  that  drawings  can 
be  made  on  both  sides,  18  x  24  in.,  per 
sheet  $1.60 

Note:  If  desired,  we  can  supply  a  Drawing 
Board,  20  x  20  in.,  together  with  Cases 
and  Paper,  for  the  same  prices  as  listed 
under  No.  573-A. 

No.  573-B  Drawing  Board,  15  x  15  in.,  with  brass 
screw  plate  fitted  and  four  clamp  screws 
and  sockets  for  paper 6.00 

Flexible  Canvas  Case  with  shoulder  strap, 

for  No.  573-B 2.50 

Eggshell  Drawing  paper,  single  mounted, 
15  x  15  in.,  per  sheet 50 

Eggshell  Drawing  Paper,  double  mounted 
(muslin  between),  so  that  drawings  can 
be  made  on  both  sides,  15  x  15  in.,  per 
sheet  1.10 

No.  573-X  Drawing  Board,  31  x  24  in.,  with  brass 
screw  plate  fitted,  and  with  eight  clamp 
screws  and  sockets  for  paper.  Especially 
constructed  for  use  in  tropical  climates, 
of  heavy  stock  and  with  expansion  cleats  11.00 
Flexible  Canvas  Case  with  shoulder  strap, 

for   No.    573-X 8.25 

No.  574        Plumbing    Arm    and    10   oz.    plummet 6.25 

No.  575        Combined    Compass    with    levels    and    square 

base    -  .     25.00 


For  Nos.  570,   570- A  or  571 

Leather  Hood  to  protect  Johnson  Tripod  Head 3.00 

Tipper  or  Lower  Wing  Nut  Clamp  Screw,  A  or  B,   each  1.60 

Keeper    Screw,     C,    each .20 

Bolt  with  Wing  Nut  and  Washer,  for  tripod  head,  each  1.10 

Wing   Nut  for   tripod  bolt,    each 45 

Extra  Board  Plate,   each 3.30 

Clamp  Screw  and  Socket  for  paper,    complete,    each. . .  .40 

Clamp   Screw   only,    each .20 

Socket    only,    each 20 

Cap  for  Johnson  Tripods  Nos.  570,  570-A  or  571 1.25 

Split  Tripod  Legs  for  No.  570,  each 3.30 

Extension  Tripod  Legs  for  No.  570,  each 7.50 

Extension  Tripod  Legs,  special  light  weight  model,  for 

No.    571,    each...  6.25 


16  W.    &  L.    E.    GITRLEY,    TEOY,    NEW   YORK 


Plane  Table  Outfits 

U,    S.    Geological    Survey    Standard 

No.  576-C  Plane  Table  Outfit,  consisting  of  Johnson 
Movement  No.  570,  with  split  leg  tripod; 
Drawing  Board  No.  573,  31  x  24  in.,  with 
brass  screw  plate  fitted,  and  with  eight 

clamp   screws   and  sockets  for  paper $54.00 

Flexible    Canvas    Case   with    shoulder    strap, 

for   No.    573   Drawing   Board 4.75 

Plumbing  Arm  and  Plummet,   No.  574 6.25 

Alidade  No.  584-C,  with  11  in.  telescope, 
inverting  eyepiece  with  diagonal  prism, 
power  about  22  diameters,  enlarged  object- 
ive, 1.38  in.  aperture,  platinum  cross  wires 
and  stadia  wires;  detachable  striding  level 
with  revolving  shield;  edge  graduated 
vertical  arc  reading  to  1  min.,  combined 
with  Beaman  Stadia  Arc;  clamp  and 
tangent  to  telescope  axis;  blade  18  x  3 
in.,  with  left  hand  edge  beveled;  circular 
level,  and  box  compass  with  4  in.  needle, 
mounted  on  blade.  In  mahogany  carrying 
case.  See  illustration  on  page  246 200.00 


Complete,    as    shown    on    page    244 265.00 

No.  576-B  Plane  Table  'Outfit,  like  Outfit  No.  576-C, 
but  with  Alidade  No.  584-B  substituted 
for  Alidade  No.  584-C 265.00 

ALIDADES,   Telescopic 

No.  584-C  Telescopic  Alidade,  as  described  above,  in 
Outfit  No.  576-C,  and  as  shown  on  page 
246  200.00 

No.  584-B  Telescopic  Alidade,  similar  to  Alidade  No. 
584-C,  but  equipped  with  an  erecting  eye- 
piece, power  about  26  diameters,  objective 

1.19    inches    aperture 200.00 

A  Gradienter  can  be  combined  with  the 
clamp  and  tangent  movement  on  Alidades 
Nos.  584-C  or  584-B,  at  an  extra  cost 
of  $18.00. 

If  Alidade  No.  584-C  or  No.  584-B  is  desired 
without  the  Beaman  Stadia  Arc  attach- 
ment, deduct  $45.00. 

Parts  (or  Alidades  Nos.  584-C  and  584-B 

No.  585        Box  Compass,   rectangular  metal  case,   4  in. 

needle,  for  Alidades  Nos.  684-B  or  584-C  12.50 

Striding  Level,  complete 20. 00 

Extra  Glass  Vial  only,  for  Striding  Level...  2.25 

Circular  Level,  complete 6.50 

Extra  Glass  Vial  only,  for  Circular  Level..  4.50 
Quarter  interval  wire,  midway  between  upper 

stadia  wire   and   horizontal   cross   wire. . .  2.75 


W.    &  L.    E.    GTJRLEY.    TROY,    NEW^  YOBK  17 

Explorers  Alidade,  Telescopic 

Price 

No.  592-C  11  in.  blade,  one  edge  beveled  and  grad- 
uated to  1/50  in.,  box  compass  with  4  in. 
needle,  circular  level,  8  in.  telescope, 
aperture  1  in.,  power  about  13  diameters, 
platinum  cross  wires  and  stadia  wires, 
spiral  movement  to  eyepiece,  pinion  move- 
ment to  objective  slide,  Gradienter,  com- 
bined with  clamp  and  tangent  to  telescope 
axis,  detachable  striding  level,  sensitive- 
ness about  90  seconds,  vertical  arc  reading 
by  vernier  to  one  minute,  vernier  movable 
by  tangent  screw,  Beaman  Stadia  Arc, 
combined  with  the  vertical  arc,  mahogany 
carrying  case.  Weight  3.25  Ibs.,  with  case 
5  Ibs.  (see  page  249) $154.00 

Extras  for  No.  592-C  Alidade 

Striding    Level    Vial,     sensitiveness    60"    or 

40"    No  extra  charge 

If  the  Beaman  Stadia  Arc  is  omitted,  deduct  22.00 

If   the   Gradienter   is   omitted,    deduct 9.00 

Special    Graduations    on    Blade,    extra 6.50 

Striding   Level,    complete 16.50 

Extra  Glass  Vial  only,   for  Striding  Level. .  1.65 

Circular   Level,    complete 5.50 

Extra  Glass  Vial  only,   for  Circular  Level..  3.85 
Quarter  interval  wire,    midway  between  the 

upper  stadia  wire  and  horizontal  cross  wire  2.75 
Leather    covered    mahogany   box    instead    of 

plain  box    10.00 

Explorers  Plane  Table  Outfits 

No.  592-D  Explorers  Plane  Table  Outfit,  consisting  of 
Johnson  Movement  No.  570,  with  split  leg 
tripod;  Drawing  Board  No.  573-A,  18  x 
24  in.,  with  brass  screw  plate  fitted,  and 
eight  clamp  screws  and  sockets  for  paper. 

Flexible   Canvas    Case   with    shoulder   strap, 
for   No.    573-A    Drawing    Board. 

Explorers  Alidade  No.  592-C,  with  Gradien- 
ter   and   Beaman    Stadia    Arc. 

Complete    210.00 

No.  592-F  Explorers  Plane  Table  Outfit,  consisting  of 
Johnson  Movement  No.  571,  special  light 
weight  model,  with  special  light  weight 
extension  leg  tripod;  Drawing  Board  No. 
573-A,  18  x  24  in.,  with  brass  screw  plate 
fitted,  and  eight  clamp  screws  and  sockets 
for  paper. 

Flexible   Canvas    Case   with    shoulder   strap, 
for   No.    573-A   Drawing    Board. 

Explorers  Alidade  No.   592-C,  with  Gradien- 
ter   and    Beaman    Stadia    Arc. 

Complete,    as  shown  on  page  249 215.00 


18  W.    &  L.    E.    GITRLEY,    TEOY,    NEW  YORK 

Price 

No.  592-H  Explorers  Plane  Table  Outfit,  consisting  of 
Johnson  Movement  No.  571,  special  light 
weight  model,  with  special  light  weight 
extension  leg  tripod;  Drawing  Board  No. 
573 -B,  15  x  15  in.,  with  brass  screw  plate 
fitted,  and  four  clamp  screws  and  sockets 
for  paper. 

Flexible  Canvas  Case  with  shoulder  strap, 
for  No.  573-B  Drawing  Board. 

Explorers  Alidade  No.  592-C,  with  Gradien- 
ter  and  Seaman  Stadia  Arc,  complete  as 
specified  on  page  249 $212.50 

Paper  for  Drawing  Boards 
Nos.  573-A  and  573-B 

For  No.  573-A    For  No.  678-B 
18  z  24  in.  15  z  15  in. 


Eggshell    Drawing     Paper,     single 

mounted,     per     sheet $0.85  $0.50 

Eggshell    Drawing    Paper,    double 

mounted    (muslin   between),    so 

that  drawings  can  be  made  on 

both   sides,    per   sheet 1.50  1.10 

Traverse   Plane  Table   Outfit 

No.  686  Consisting  of  Traverse  Movement  No.  587, 
with  solid  round  tripod  legs;  No.  573-T 
Drawing  Board,  15  x  15  in.,  with  spring 
board  plate,  Box  Compass  No.  588  in- 
serted in  one  edge,  and  four  clamp 
screws  and  sockets  for  paper;  Ruler  Sight 
Alidade  No.  589,  with  graduated  edge, 
folding  sights  and  leather  pouch;  com- 
plete as  shown  on  page  257 38.50 

Extras  for  Traverse  Plane  Table 

Extension    Leg    Tripod,    instead    of    Solid    Round    Leg 

Tripod,     extra     6.50 

Jointed  Extension  Leg   Tripod,   closing  to  23   in.,   with 

canvas  case,    instead  of  Solid  Round  Leg  Tripod,  extra    16.00 
Flexible  Canvas  Case  with  shoulder  strap,  for  Drawing 

Board    No.     573-T,     extra 2.50 

Eggshell  Drawing  Paper,   single  mounted,    15  x  15  in., 

per  sheet    50 

Eggshell   Drawing   Paper,    double   mounted    (muslin   be- 
tween),   so    that    drawings    can    be    made    on    both 

sides,    15   z   15    in.,    per   sheet 1.10 

No.  587  Traverse  Plane  Table  Movement,  with  solid 
round  leg  tripod;  Drawing  Board,  15  x  15 
inches,  with  spring  board  plate,  and  four 
clamp  screws  and  sockets  for  paper. ...  16.50 
No.  573-T  Drawing  Board,  15  x  15  in.,  with  spring 
plate  fitted,  and  with  four  clamp  screws 
and  sockets  for  paper 6.00 


W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK      19 

Price 
No.  588        Box  Compass,  rectangular  metal  case,  4  in. 

needle    $10.00 

No.  589  Ruler  Sight  Alidade,  10  in.  long,  with  grad- 
uated edge,  folding  sights  and  leather 

pouch     15.00 

Spring   Plate   for   Drawing   Board,    each 2.50 

Center  Plunger   Clamp   Screw,    complete,    each 3.00 

Clamp  Screw   and  Socket  for  paper,    complete,   each...         .40 

Solid    Round    Tripod    Legs,     each 1.75 

Extension    Tripod    Legs,    each 4.00 

Bolt,  with  wing  nut  and  washer,  for  tripod  head,  each      1.00 
Wing   Nut   for  tripod   bolt,    each 45 

Pocket  Sight  Alidade 

No.  590- A  Pocket  Alidade,  6  in.  long,  with  graduated 
edge  and  folding  sights,  and  with  leather 
case  having  pencil  pockets  (see  page  259)  9.50 

No.  590-B  Extra  Folding  Sights,  for  Alidade  No. 

590-A,  per  pair 4.00 

SKETCHING  CASES 

No.  594  Army  Sketching  Case,  Glenn  S.  Smith  Model, 
with  one  Protractor  card,  as  selected 
(see  page  261) 25.00 

Extras  for  the  Above 

Extra  Protractor   Cards,    each 1.00 

Distance  between  each  circle 

Scale  A,   1  inch  to  1   mile          132  ft.,  or  1/40    mile 
'Scale  B,  2  inches  to  1  mile          66ft.,  or  1/80    mile 
Scale  C,  3  inches  to  1  mile        52.8  ft.,  or  1/100  mile 
Scale  D,   1  to  24,000  1/100  mile 

and  and 

1  to  48,000  1/50  mile 

Scale  F,   1  to  100,000  Metric        100  meters  (10  to  1  kilo) 
*Scale  B  is  also  suitable  for  a  map  scale,   1 
inch  to  400  feet,   each  circle  representing 
10  feet  distance. 
Flexible  Canvas  Pouch,   with  leather  shoulder  strap...       2.25 

Sole   Leather   Pouch,    with   shoulder    strap 7.50 

Tripod,   with  solid  round  legs 4.50 

Staff,  2  ft.  long,  with  metal  shoe 1.25 

Vellum  Tracing  Paper,  in  rolls,   8  x  36  in.,  per  roll...         ,10 
Translucent  Celluloid,  in  rolls,  8%  x  50  in.,  per  roll...         .75 
Celluloid  is  more  durable  than  paper  and  not  affected 
by  moisture. 

No.  596        Fiala    Scout    Sketching    Case 7.50 

Architects     Drawing     Paper,     in     rolls     5% 
x    36   in.,    per   roll,    postpaid .05 


20  W.    &  L.    E.    GTJTILEY^  TROY.    NEW  YORK 

CURRENT  METERS 
Acoustic  Current  Meter 

No.  616  Acoustic  Current  Meter,  indicating  each 
10th  revolution,  equipped  with  rubber 
tube,  ear  piece  and  connection;  also  two 
lengths  of  sleeve  jointed  wading  rod, 
graduated  to  measure  4  ft.  from  plane 
of  bucket  wheel.  Wooden  case  with  lock 
and  strap  and  including  accessories  of 
oil  can,  wrench,  screw  driver  and  pivot 
bearing  (see  page  277) $66.00 

Accessories  (or  No.  616 

Wading  Rod,  sleeve-jointed  and  graduated, 
per  2  ft.  length 3.50 

Canvas  Case  for  two,  three  or  four  lengths 

of  Rod  4.50 

Time  Recorder,  or  Stop  Watch,  No.  619, 
open  face,  nickel  case,  stem  winder,  with 
fly-back  attachment  for  starting  and 
stopping.  Registering  minutes,  seconds 
and  fifths  of  seconds 10.00 

Electric  Current  Meters 

No.  623  Electric  Current  Meter  with  two  inter- 
changeable commutator  boxes,  one  indi- 
cating each  revolution  and  the  other 
indicating  each  fifth  revolution  of  the 
bucket  wheel,  Covert  Yoke,  telephone 
sounder,  dry  battery,  20  ft.  of  cable,  10 
Ib.  lead  weight  and  weight  hanger.  All 
packed  in  wooden  box  with  lock,  hooks 
and  strap  and  including  accessories  of  oil 
can,  wrench,  screw  driver,  extra  pivot 
bearing,  binding  screws  and  nipple  (see 
page  280)  110.00 

No.  617  Electric  Current  Meter.  This  is  like  No. 
623,  except  that  it  has  only  one  com- 
mutator box  indicating  each  revolution 
of  the  bucket  wheel 93.50 

No.  621  Electric  Current  Meter.  This  is  like  No. 
623,  except  that  it  has  only  one  com- 
mutator box  indicating  each  fifth  revolu- 
tion of  the  bucket  wheel 93.50 

Accessories  for   Current  Meters 
Nos.  617,  621  and  623 

Extra  Cable,  per  foot .15 

Extra  Dry  Cell  Battery .35 

Extra  Lead  Weight,    10  Ibs 5.00 

Extra  Lead  Weight,    15  Ibs 6.25 

Time  Recorder,   or  Stop  Watch,    No.    619,    as  described 

above  under  Meter  No.   616 10.00 


W.    &  L.    E.    QURLEY.    TROY,    NEW  YORK  81 

Price  Postage 
Wading  Rods,   sleeve-jointed  and  graduated,   per  2  ft. 

length    $3.50 

Wading  Rods,  flush-jointed  and  graduated,  for  use  with 

double-end  Hanger,    per  2  ft.    length 3.50 

Wading    Rods,    flush- jointed,    4    sections,    graduated    to 

measure    8    feet    from    plane    of    bucket    wheel,    at 

$3.25    per   section 14.00 

Double-end  Hanger,   for  use  with   flush-jointed   Rods..  4.00 

Base,   for  use   with   Rod 2.75 

Leather  Case  for  rods,  base  and  hanger 13.00 

Canvas  Case  for  rods,   base   and  hanger 4.50 

Electric  Register,  No,  609,  as  described  on  page  281...  30.00 

ELECTRIC  REGISTER 

No.  609         (See   page   281) 30.00 

HOOK  GAGE 

No.  628        (See   page   283) 25.00 

WATER  STAGE  REGISTERS 

No.  630  Printing  Register  (see  page  290) 385.00 

No.  632  Tape  Reel  for  use  with  No.  630  Register. .  27.50 
No.  633  Graphic  Register  with  spring  driven  clock 

(see  page  293) 145.00 

No.  636  Graphic  Register,  with  weight  driven  clock  145.00 
No.  634  Graphic  Register,  with  spring  driven  clock, 

range  0  to  1  ft.,  time  scale  7  days 95.00 

No.  634-A  Graphic  Register,  range  0  to  2  ft.,  time 

scale  7  days 110.00 

LONG  DISTANCE 
WATER  STAGE  REGISTER 

No.  637  Long  Distance  Register    (see   page   296) 275.00 

No.  638  Long  Distance  Sender    (see    page    299) 110.00 

No.  639  Long  Distance  Indicator    (see    page    300) ....   155.00 

No.  639-A  Indicating   Gage    (see  page  301) 55.00 

PRECISION  BALANCE 

No.  9570       (See   page   303) 450.00 

Miscellaneous  Instrument  Parts  and  Supplies 

Prices  of  Parts  for  Gurley  Instruments, 
Liable  to  Loss  or  Injury 

Solid   Round    Tripod   Legs   only,    for   Engineers    Transit 

or    Level,    per    set 7.50 

Split  Tripod  Legs  only,  for  Engineers  Transit  or  Level, 

per  set    12.50 

Extension   Tripod  Legs   only,    for  Engineers   Transit   or 

Level,     per    set 16.00 

Clamp  Screw  and  Band  for  extension  tripod  leg,   each      1.25     .05 
Tripod  Head  only,   with  bolts  and  nuts,   for  Engineers 

Transit    or    Level 7.50     .50 

Cap  for  tripod  head,   each 1.25     .12 


22 W.  &  L.  E.  GURLEY,  TROY,  NEW  YORK 

Price  Postage 

Brass  Bolt  and  Nut  to  fit  tripod  head,  each $1.00  .05 

Metal  Point  or  Shoe  for  tripod  leg,  each 65  .05 

Shawl  Strap  (superior),  for  extension  tripod 1.25  .10 

Steel  Screw  Driver  with  wooden  handle,  each .35  .05 

Steel  Adjusting  Pins,  each 08  .01 

Steel  Adjusting  Pins,  with  eye,  for  attaching  to  key 

ring,  each  .20  .02 

Rubber  Tips,  for  bottom  of  instrument  box,  per  set...  .80  .08 

Leather  Strap  and  Buckle  for  transit  box 1.00  .10 

Leather  Strap  and  Buckle  for  level  box 1.25  .10 

Lock  and  Key  for  instrument  box 1.00  .03 

Reading  Glass  for  transit,  each 1.25  .02 

Brass  Plummet  with  screw  cap,  for  transit  or  level, 

each  2.00  .20 

Waterproof  Hood,  for  transit  or  level,  each 1.25  .06 

Clamp  with  Clamp  Screw,  for  New  York  Rod 3.25  .15 

Clamp  with  Scale  and  Clamp  Screw,  for  Philadelphia 

Rod  4.00  .15 

Target  with  Clamp  Screw  and  Spring,  for  New  York 

or  Philadelphia  Rod 4.00  to  8.50  .35 

Chain  Handle,  with  staple  and  nuts,  each 1.00  .08 

Chain  Tallies,  per  set  of  9 .65  .06 

Instrument  Oil,  finest  grade,  small  bottle 45  .05 

Camel  Hair  Brush 1.25  .02 

Parts   for   Gurley   Transits 

Needle  with  jeweled   center  and   center  pin 5.00     .12 

Center    Pin    only .75     .01 

Ground   Glass  Level  Vials,   for  platet  each 1.25     .02 

Ground    Glass    Level    Vials,    brass    mounted    complete, 

for   plate,    each 3.00     .14 

Ground    Glass    Level    Vial,    for    telescope,    unmounted, 

2.75  to  3.50     .14 

Cap  for  eyepiece  or  object  glass,   each 1.00    .03 

Shade    for    object    glass 1.00     .03 

Clamp   Screws   for   horizontal   limb,    each 1.00     .02 

Tangent   Screw   for   leveling   head 1.00  to  2.00     .13 

Claim*    Screw    for    leveling    head 1.00     .03 

Leveling  Screw  for  leveling  head,    each 1.25  to  2.00     .14 

Eyepiece    complete,    including  lenses    and   settings,    and 

omitting    cap    8.00     .14 

Object     Glass     complete 8.00     .14 

Platinum   Cross   Wires    and   Diaphragm 4.50     .15 

Platinum   Stadia   Wires,    adjustable,    and   diaphragm...       8.00     .15 

Platinum   Stadia   Wires,    fixed,    and    diaphragm 10.00     .15 

Platinum   Cross  Wires  only  fitted  to  old  diaphragm...       3.50 
Platinum    Cross    Wires    and    adjustable    Stadia    Wires 

fitted    to    old    diaphragm 6.00 

Platinum    Cross    Wires    and    fixed    Stadia    Wires    fitted 

to   old   diaphragm 8.00 

Brass    packing    box    for    mailing     any     of     the     above 

diaphragms    .50 

*Mahogany  Box  with  lock  and  strap,   and  fitted  inside, 

according    to    size $12.00  to  15.00 

*When  ordering,  specify  length  of  telescope, 
length  of  compass  needle,  height  of  the  instru- 
ment from  bottom  plate  of  the  leveling  head  to 
the  tops  of  the  standards,  and  also  state  whether 


W.    &   L.    E.    GTTRLEY.    TEOY,    NEW   YORK  88 

Price  Postage 

it  has  a  vertical  arc  or  a  full  vertical  circle. 
Unless  the  Transit  is  sent  to  us,  the  new  box 
will  be  furnished  with  the  packing  pieces  or 
blocks  not  fitted  in  position. 

Plummet  Screw  and  Chain  for  bottom  of  leveling  head.     $0.45  .04 

Adjusting    Pins,    each 08  .01 

Adjusting   Pins,    with   eye    for   attaching    to    key   ring, 

each    20  .02 

Screw  driver,    small  size .35  .04 

Screw   driver,    large    size 65  .08 

Waterproof   Hood    1.25  .10 

Instrument    Oil,    finest   grade,    small   bottle 45  .05 

Parts  for  Gurley  Wye  Levels 

Ground  Glass  Level  Vial,  unmounted,  graduated  and 

figured,  for  22-inch  Wye  Level 5.00  .25 

Ground  Glass  Level  Vial,  unmounted,  not  graduated  or 

figured,  for  22-inch  Wye  Level 4.50  .25 

Ground  Glass  Level  Vial,  unmounted,  graduated  and 

figured,  for  15-inch,  18-inch  or  20-inch  Wye  Level  4.50  .20 

Ground  Glass  Level  Vial,  unmounted,  not  graduated  or 

figured,  for  15-inch,  18-inch  or  20-inch  Wye  Level  4.00  .20 

Ground  Glass  Level  Vial,  unmounted,  extra  sensitive 
(value  of  each  graduation  10  seconds),  graduated 
and  figured,  for  18-inch,  20-inch  or  22-inch  Wye 
Level  10.00  .25 

Ground  Glass  Level  Vial,  unmounted,  extra  sensitive 
(value  of  each  graduation  10  seconds),  not  grad- 
uated or  figured,  for  18-inch,  20-inch  or  22-inch 
Wye  Level  9.50  .25 

Ground  Glass  Level  Vial,  unmounted,  for  Architects 

Level  2.25  .05 

Note:  Whenever  possible  the  metal  case  or  tube 
should  be  sent  us  so  that  the  vial  can  be  properly 
set.  The  extra  cost  is  75  cents. 

Cap   for  eyepiece   or   object   glass,    each 1.00  .03 

Clamp    Screw    for    leveling    head 1.00  .03 

Tangent    Screw    for    leveling    head 1.50  to  2.00  .13 

Leveling  Screw   for  leveling  head,    each 1.50  to  2.75  .14 

Eyepiece   complete,    including   lenses    and   settings,    and 

omitting    cap    8.00  .14 

Object    Glass,    complete 10.00  .14 

Platinum    Cross   Wires   and   Diaphragm 4.50  .15 

Platinum   Adjustable   Stadia   Wires,    Cross   Wires,    and 

Diaphragm     8.00  .15 

Platinum  Fixed  Stadia  Wires,  Cross  Wires,  and  Dia- 
phragm    10.00  .15 

"•Mahogany  Box  with  lock  and  strap,  and  fitted  inside, 

according    to    size $7.50  to  15.00 

*Note:  When  ordering,  specify  the  exact  length 
of  the  telescope  when  both  the  eyepiece  and  the 
objective  slides  are  not  extended;  also  state  the 
height  of  the  instrument  from  the  bottom  plate 
of  the  leveling  head  to  the  top  of  the  wyes 
and  mention  the  diameter  of  the  bottom  plate 
of  the  leveling  head.  Unless  the  Level  is  sent 


24  W.    &  L.    E.    GTTRLEY,    TROY.    NEW   YORK 

Price  Postage 

to  us,    the   new   box   will   be   furnished   with   the 
packing   pieces   or  blocks   not   fitted    in   position. 

Adjusting   Pins,    each $0.08  .01 

Adjusting    Fins,    with    eye    for   attaching    to    key    ring, 

each    20  .02 

Parts  for  Surveyors   Compasses 

with  4  in.,  5  in.  or  6  in.  needle, 

like  model  No.  226 

Needle   with   jeweled   center   and   center   pin 5,00  .12 

Center  pin  only 75  .01 

Ground  glass  level  vials,    each 60  .02 

Ground  glass  level  vials,  brass,  mounted,  complete,  each      2.50  .14 

Brass  cover  for  compass  of  our  make 1.25  .25 

Outkeeper    1.25  .13 

Glass  circle,   unmounted,   old  style  flat  glass,  for  com- 
pass   face    35  .15 

Glass  circle,  unmounted,  new  style,  beveled  edge  plate 

glass,     for     compass    face 2.00  .15 

Wrench    for    center    pin .15  .01 

Staff  mountings,  brass  head  and  clamp,  without  spindle      2.50  .25 

Staff     mountings,     steel     point 65  .18 

Cap   only   for  staff  socket   or   tripod  head 1.00  .12 

Ball  spindle  fitted  to  new  or  old  socket 4.00  .30 

Sight    vanes    only,    each 3.00  .20 

Clamp  screw  for  spindle  or  sight  vane .65  .03 

Socket  complete,   including  clamp   screw,   spring  catch, 

needle    lifting    screw    and    lifter 10.00  .50 

Needle    lifter    50  .05 

Needle    lifting    screw 65  .05 

Spring    catch    65  .05 

Bolt  with   nut  and   washer  for   tripod  head .85  .05 

Nut   and  washer   for   tripod   bolt 40  .04 

Mahogany   box   with    lock    and    strap 7.50 

Parts  for  Compasses  Nos.  285  and  294 

Needle  with  jeweled  center  and  center  pin 5.00  .12 

Center  pin  only .75  .02 

Glass  Circle,  unmounted,  beveled  edge  plate  glass  for 

No.  285  2.00  .15 

Glass  circle,  unmounted,  for  No.  294 ,35  .15 

Plate  level  vials  only  for  No.  285,  each 1.25  .05 

Plate  level  vials  with  case  and  adjusting  screws  for 

No.  285,  each 3.00  .14 

Plate  level  vials  only  for  No.  294,  each 50  .04 

Plate  level  vials  with  case  and  adjusting  screws  for 

No.  294,  each 1.50  .10 

Telescope  level  vial  only  for  No.  294 3.00  .14 

Telescope  level  complete  for  No.  294 7.50  .25 

Folding  sights  for  No.  285,  each 6.00  .15 

Tangent  screw  and  nut  for  any  movement 1.50  .12 

Opposing  spring  plunger  and  case  for  tangent  screw. .  1.25  .05 

Clamp  screw  for  telescope  axis .65  .05 

Clamp  screw  for  limb  or  leveling  head 1.00  .05 

Leveling  screw  for  No.  294 1.25  .05 

Dust  cap  for  leveling  screw 50  .03 


W.  &  L.  E,  GITRLEY,  TROY,  NEW  YORK 26 

Price  Postage 

Dust  cap  or  sunshade  for  objective,  each $1.00  .05 

Eyepiece  cap  1.00  .05 

Spindle  and  socket,  clamp  screw  and  cap  for  Jacob 

staff  socket  or  tripod  for  No.  285 4.00  .20 

Spindle  and  socket  and  clamp  screw,  without  cap  for 

No.  285  3.25  .17 

Jacob  staff  socket  and  cap  for  No.  285 1.50  .15 

Cap  only  for  Jacob  staff  socket  or  tripod  for  No.  285  .75  .08 

Shoe  for  Jacob  staff  or  tripod  leg .65  .05 

Bolt  with  nut  and  washer  for  tripod  head 85  .05 

Nut  and  washer  for  tripod  bolt .40  .04 

Mahogany  box  for  No.  285 5.00  .30 

Mahogany  box  for  No.  294 , 12.00  .60 

Parts  for  Pocket   Compasses 
Nos.  300,  305,  335  and  350 

Needle  with  jeweled  center  and  center  pin 5.00  .12 

Center  pin  only 75  .02 

Level  vials  only,  each .50  .04 

Level  vials  with  case  and  adjusting  screws,  each 1.50  .10 

Glass  circle  35  .15 

Folding  sights  for  No.  305,  each 4.00  .17 

Folding  sights  for  Nos.  300,  335,  and  350,  each 3.50  .17 

Removable  sight  for  No.  350 2.00  .12 

Needle  lifting  screw 35  .02 

Clamp  nut  for  variation  arc 25  .02 

Clamp  nut  for  spindle .35  .02 

Spindle  and  socket,  clamp  screw  and  Jacob  staff  socket 

with  cap,  for  Nos.  300,  335  and  350 3.00  .15 

Spindle  and  socket,  clamp  screw  and  Jacob  staff  socket 

with  cap  for  No.  305 4.50  .20 

Jacob  staff  socket  and  cap  for  Nos.  300,  335  and  350..  1.00  .15 

Jacob  staff  socket  and  cap  for  No.  305 1.50  .15 

Cap  only  for  staff  socket  or  tripod  for  Nos.  300,  335 

and  350  50  .06 

Cap  only  for  staff  socket  or  tripod  for  No.  305 .75  .08 

Shoe  for  Jacob  staff  or  tripod  leg 65  .05 

Bolt  with  nut  and  washer  for  tripod  head ,85  .05 

Nut  and  washer  for  tripod  bolt 40  .04 

Mahogany  box  for  No.  300,  335  and  350 3.00  .20 

Mahogany  box  for  No.  305 3.50  .25 

CHAINS 

Made  by  W.  &  L.  E.   Gurley 
Brazed  Steel  Chains 

No.  670        33  ft.,  50  links,  No.  12  tempered  steel  wire, 

brazed  links  and  rings 5.75  .45 

No.  671  50  ft.,  50  links,  No.  12  tempered  steel  wire, 

brazed  links  and  rings 7.00  .55 

No.  672  66  ft.,  100  links,  No.  12  tempered  steel 

wire,  brazed  links  and  rings 10.50  .70 

No.  673  100  ft.,  100  links,  No.  12  tempered  steel 

wire,  brazed  links  and  rings 11.501.00 

Steel  Snaps  to  make  full  chains  into  half 

chains,   without   extra   charge,    if   ordered 

with   the   chain. 


W.   &  L.  E.   GURLEY,   TROY,  NEW  YORK 


No.  708 
No.  710 


No.  730 
No.  732 


No.  740 
No.  743 

No.  749 


No.  774 
No.  776 


V  -     20 
V  -     30 


No.  782 
No.  786 


Vara  Chains    (1    vara     33.333   inches) 

Price  Postage 

10  varas,  50  links,   oval  rings,   No.    12  tem- 
pered  steel   wire,    brazed   links   and   rings     $5.75     .35 
20  varas,  100  links,   oval  rings,  No.   12  tem- 
pered   steel    wire,    brazed   links   and   rings     10.50     .65 

Meter  Chains  (1  meter     39.371  inches) 

10  meters,  50  links,  oval  rings,  No.  12  tem- 
pered steel  wire,  brazed  links  and  rings  5.75  .45 

20  meters,  100  links,  oval  rings,  No.  12  tem- 
pered steel  wire,  brazed  links  and  rings  10.50  .70 

Marking   Pins 

Set  of  11  Pins,  No.  4  iron  wire,  nickel- 
plated,  14  in.  long 1.45  .50 

Set  of  11  Pins,  3/16  steel  wire,  14  in.  long, 
japanned  red  and  white,  alternating  each 
inch.  Quickly  located  in  brush  or  grass  2.00  .40 

Spring  Steel  Carrying  Ring  for  marking  pins        .30 

TAPES 
Steel  Ribbon  Chain  Tapes 

One-quarter  inch  wide,  heavy  steel  ribbon, 
deeply  etched  graduations,  large  detach- 
able handles  and  wooden  reel  with  nickel- 
ed trimmings. 

Steel  Ribbon,  66  ft.,  graduated  to  100  links  7.00  .40 
Steel  Ribbon,  100  ft.,  graduated  each  foot  8.50  .50 
The  66  foot  tape  has  the  first  and  last  links 

in  lOths. 

The  100  foot  tape  has  the  first  and  last  feet 
in  lOths. 

Metric  Measure  Only 

Steel  Ribbon,  20  meters,  graduated  to  deci- 
meters    6.00 

Steel  Ribbon,  30  meters,  graduated  to  deci- 
meters    9.25 

These  tapes  have  the  first  meter  in  centi- 
meters with  the  first  decimeter  in  milli- 
meters. 

Vara  Measure  Only 

Steel  Ribbon,  20  varas,  graduated  to  tenths 
of  a  vara 8.50 

Steel  Ribbon,  30  varas,  graduated  to  tenths 
of  a  vara 10.50 


.40 
.50 


.40 
.45 


Metallic  Tapes 

Metallic  Tape,  50  ft.,  in  lOths  or  12ths, 

and  links  4.25 

Metallic  Tape,  100  ft.,  in  lOths  or  12ths, 

and  links  .  7.00 


.30 


W.  &  L.   E.   GURLEY,   TROY,   NEW  YORK 


Metallic  Tapes  without  Cases 

Price  Postage 

These    tapes    can    be    put    into    the    leather 
cases  when  the  original  tape  line  is  worn 
out. 
No.  791        Metallic    Tape,    50    ft.,    in    lOths    or    IZths, 

and    links    $2.50     .16 

No.  794        Metallic    Tape,    100    ft.,    in    lOths    or    12ths, 

and    links    5.00     .20 

We  can  furnish  Metallic  Tapes  Nos.  791 
and  794,  with  metric  or  vara  measure  on 
reverse  side,  instead  of  links  at  an  extra 
cost  of  two  cents  per  foot. 

Reliable  Steel  Tapes  (Best  Quality) 
Instantaneous   Readings 

Three-eighths  inch  wide,  in  leather  case  with 
nickeled     trimmings     and     double     folding 
flush    handle    opened   by   pressing    on    op- 
posite  side. 
No.  798        Steel    Tape,     100    ft.,     in    lOths    or    12ths, 

and    links     14.75     .30 

Tape  No.  798  can  be  furnished  with  metric 
or  vara  measure  on  reverse  side,  instead 
of  links,  at  an  extra  cost  of  two  cents 
per  foot. 

Reliable  Junior   Steel  Tapes, 
Instantaneous   Readings 

One-quarter  inch  wide,  in  leather  case  with 
nickeled  trimmings  and  double  folding 
flush  handle  opened  by  pressing  on  op- 
posite side. 

A  convenient  vest  pocket  tape,  being  an 
exact  counterpart  of  the  "Reliable,"  and 
not  much  over  one-half  its  size  and  weight. 

No.  800        Steel   Tape,    25    ft.,    in   lOths   or   12ths 4.75     .15 

No.  801        Steel    Tape,    50   ft.,    in   lOths   or   12ths 7.25     .20 

Tapes  Nos.  800  and  801  supplied  with  vara, 
metric  measure,  or  links  on  reverse  side, 
at  an  extra  cost  of  two  cents  per  foot. 

Wolverine   Steel   Tapes, 
Instantaneous   Readings 

One-quarter  inch  wide,  with  open  metal  reel 

having   folding    handle    and   leather    strap 

on   reverse   side,    by   which    the    tape    can 

be    firmly   held    when    winding. 

No.  817        Steel    Tape,     100    ft.,    in    lOths    or    12ths, 

and    links    18.00     .35 

Tape  No.  817  supplied  with  vara  or  metric 
measure  on  reverse  side,  instead  of  links, 
without  extra  charge. 


28 W.   &  L.  E.  GITRLEY,   TROY,  NEW  YORK 

Engineers  Pattern  Steel  Tapes  (Best  Quality) 
Instantaneous   Readings 

Price  Postage 

One-quarter   inch   wide,    in   cases   with   fold- 
ing flush  handles,  opened  by  pressing  pin 
on  opposite  side.  Nickel-plated  trimmings. 
No.  824        Steel    Tape,     100    ft.,     in    lOths    or    12th s, 

and    links    $14.50     .85 

In   metal   lined   hard   leather   case. 
No.  835        Steel    Tape,     100    ft.,     in    lOths    or    12ths, 

and    links    13.50     .35 

In  black  enameled  steel  case. 

Tapes  Nos.  824  and  835  are  detachable  from 
their  cases  and  are  furnished  with  an 
extra  handle,  No.  841,  and  can  be  used 
as  a  chain  tape. 

They  are  graduated  to  feet,  tenths  and 
hundredths  of  feet,  or  to  feet,  inches  and 
eighths  of  inches,  as  desired,  on  one  side, 
and  to  links  and  poles,  vara  or  metric, 
as  desired,  on  the  reverse  side. 

Tape  Repair  Outfits 

No.  885        Punch   and   Eiveter,    with    two   packages    of 

eyelets     4.50    .30 

This  Punch  cuts  a  clean  hole  in  steel  tapes 
of  the  usual  thickness,  and  the  eyelet  is 
then  inserted  and  quickly  'and  neatly 
riveted.  The  punch  is  7%  inches  long. 
For  the  repair  of  all  tapes  except  heavy 
ribbon  chain  tapes. 
No.  887  Eureka  Tape  Repair  Sleeves.  One  dozen 

sleeves     60    .05 

Half -Dozen     sleeves 40    .05 

These  sleeves  of  thin  sheet  metal  are 
coated  with  a  combination  of  solder  and 
flux  so  sensitive  that  they  make  a  per- 
fect adhesion  with  the  tape  by  the  heat 
of  a  lighted  match.  The  repair  can  be 
made  in  the  field  in  one  minute.  Com- 
plete directions  accompany  each  set. 

When  ordering,  be  sure  to  specify  width  of 
tape  and  if  heavy  or  light  ribbon. 


YB  24058 


W.  &L 


800336 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


